##############################################################
menu.printf=AVR printf Version
menu.scanf=AVR scanf Version
yun.menu.printf.default=Default printf
yun.menu.printf.default.avr_printf_flags=
yun.menu.printf.full=Full printf
yun.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
yun.menu.printf.minimal=Minimal printf
yun.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
yun.menu.scanf.default=Default scanf
yun.menu.scanf.default.avr_scanf_flags=
yun.menu.scanf.full=Full scanf
yun.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
yun.menu.scanf.minimal=Minimal scanf
yun.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
yun.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
uno.menu.printf.default=Default printf
uno.menu.printf.default.avr_printf_flags=
uno.menu.printf.full=Full printf
uno.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
uno.menu.printf.minimal=Minimal printf
uno.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
uno.menu.scanf.default=Default scanf
uno.menu.scanf.default.avr_scanf_flags=
uno.menu.scanf.full=Full scanf
uno.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
uno.menu.scanf.minimal=Minimal scanf
uno.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
uno.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
diecimila.menu.printf.default=Default printf
diecimila.menu.printf.default.avr_printf_flags=
diecimila.menu.printf.full=Full printf
diecimila.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
diecimila.menu.printf.minimal=Minimal printf
diecimila.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
diecimila.menu.scanf.default=Default scanf
diecimila.menu.scanf.default.avr_scanf_flags=
diecimila.menu.scanf.full=Full scanf
diecimila.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
diecimila.menu.scanf.minimal=Minimal scanf
diecimila.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
diecimila.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
nano.menu.printf.default=Default printf
nano.menu.printf.default.avr_printf_flags=
nano.menu.printf.full=Full printf
nano.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
nano.menu.printf.minimal=Minimal printf
nano.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
nano.menu.scanf.default=Default scanf
nano.menu.scanf.default.avr_scanf_flags=
nano.menu.scanf.full=Full scanf
nano.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
nano.menu.scanf.minimal=Minimal scanf
nano.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
nano.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
mega.menu.printf.default=Default printf
mega.menu.printf.default.avr_printf_flags=
mega.menu.printf.full=Full printf
mega.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
mega.menu.printf.minimal=Minimal printf
mega.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
mega.menu.scanf.default=Default scanf
mega.menu.scanf.default.avr_scanf_flags=
mega.menu.scanf.full=Full scanf
mega.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
mega.menu.scanf.minimal=Minimal scanf
mega.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
mega.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
megaADK.menu.printf.default=Default printf
megaADK.menu.printf.default.avr_printf_flags=
megaADK.menu.printf.full=Full printf
megaADK.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
megaADK.menu.printf.minimal=Minimal printf
megaADK.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
megaADK.menu.scanf.default=Default scanf
megaADK.menu.scanf.default.avr_scanf_flags=
megaADK.menu.scanf.full=Full scanf
megaADK.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
megaADK.menu.scanf.minimal=Minimal scanf
megaADK.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
megaADK.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
leonardo.menu.printf.default=Default printf
leonardo.menu.printf.default.avr_printf_flags=
leonardo.menu.printf.full=Full printf
leonardo.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
leonardo.menu.printf.minimal=Minimal printf
leonardo.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
leonardo.menu.scanf.default=Default scanf
leonardo.menu.scanf.default.avr_scanf_flags=
leonardo.menu.scanf.full=Full scanf
leonardo.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
leonardo.menu.scanf.minimal=Minimal scanf
leonardo.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
leonardo.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
micro.menu.printf.default=Default printf
micro.menu.printf.default.avr_printf_flags=
micro.menu.printf.full=Full printf
micro.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
micro.menu.printf.minimal=Minimal printf
micro.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
micro.menu.scanf.default=Default scanf
micro.menu.scanf.default.avr_scanf_flags=
micro.menu.scanf.full=Full scanf
micro.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
micro.menu.scanf.minimal=Minimal scanf
micro.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
micro.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
esplora.menu.printf.default=Default printf
esplora.menu.printf.default.avr_printf_flags=
esplora.menu.printf.full=Full printf
esplora.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
esplora.menu.printf.minimal=Minimal printf
esplora.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
esplora.menu.scanf.default=Default scanf
esplora.menu.scanf.default.avr_scanf_flags=
esplora.menu.scanf.full=Full scanf
esplora.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
esplora.menu.scanf.minimal=Minimal scanf
esplora.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
esplora.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
mini.menu.printf.default=Default printf
mini.menu.printf.default.avr_printf_flags=
mini.menu.printf.full=Full printf
mini.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
mini.menu.printf.minimal=Minimal printf
mini.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
mini.menu.scanf.default=Default scanf
mini.menu.scanf.default.avr_scanf_flags=
mini.menu.scanf.full=Full scanf
mini.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
mini.menu.scanf.minimal=Minimal scanf
mini.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
mini.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
ethernet.menu.printf.default=Default printf
ethernet.menu.printf.default.avr_printf_flags=
ethernet.menu.printf.full=Full printf
ethernet.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
ethernet.menu.printf.minimal=Minimal printf
ethernet.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
ethernet.menu.scanf.default=Default scanf
ethernet.menu.scanf.default.avr_scanf_flags=
ethernet.menu.scanf.full=Full scanf
ethernet.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
ethernet.menu.scanf.minimal=Minimal scanf
ethernet.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
ethernet.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
fio.menu.printf.default=Default printf
fio.menu.printf.default.avr_printf_flags=
fio.menu.printf.full=Full printf
fio.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
fio.menu.printf.minimal=Minimal printf
fio.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
fio.menu.scanf.default=Default scanf
fio.menu.scanf.default.avr_scanf_flags=
fio.menu.scanf.full=Full scanf
fio.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
fio.menu.scanf.minimal=Minimal scanf
fio.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
fio.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
bt.menu.printf.default=Default printf
bt.menu.printf.default.avr_printf_flags=
bt.menu.printf.full=Full printf
bt.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
bt.menu.printf.minimal=Minimal printf
bt.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
bt.menu.scanf.default=Default scanf
bt.menu.scanf.default.avr_scanf_flags=
bt.menu.scanf.full=Full scanf
bt.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
bt.menu.scanf.minimal=Minimal scanf
bt.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
bt.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
LilyPadUSB.menu.printf.default=Default printf
LilyPadUSB.menu.printf.default.avr_printf_flags=
LilyPadUSB.menu.printf.full=Full printf
LilyPadUSB.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
LilyPadUSB.menu.printf.minimal=Minimal printf
LilyPadUSB.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
LilyPadUSB.menu.scanf.default=Default scanf
LilyPadUSB.menu.scanf.default.avr_scanf_flags=
LilyPadUSB.menu.scanf.full=Full scanf
LilyPadUSB.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
LilyPadUSB.menu.scanf.minimal=Minimal scanf
LilyPadUSB.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
LilyPadUSB.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
lilypad.menu.printf.default=Default printf
lilypad.menu.printf.default.avr_printf_flags=
lilypad.menu.printf.full=Full printf
lilypad.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
lilypad.menu.printf.minimal=Minimal printf
lilypad.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
lilypad.menu.scanf.default=Default scanf
lilypad.menu.scanf.default.avr_scanf_flags=
lilypad.menu.scanf.full=Full scanf
lilypad.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
lilypad.menu.scanf.minimal=Minimal scanf
lilypad.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
lilypad.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
pro.menu.printf.default=Default printf
pro.menu.printf.default.avr_printf_flags=
pro.menu.printf.full=Full printf
pro.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
pro.menu.printf.minimal=Minimal printf
pro.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
pro.menu.scanf.default=Default scanf
pro.menu.scanf.default.avr_scanf_flags=
pro.menu.scanf.full=Full scanf
pro.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
pro.menu.scanf.minimal=Minimal scanf
pro.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
pro.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
atmegang.menu.printf.default=Default printf
atmegang.menu.printf.default.avr_printf_flags=
atmegang.menu.printf.full=Full printf
atmegang.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
atmegang.menu.printf.minimal=Minimal printf
atmegang.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
atmegang.menu.scanf.default=Default scanf
atmegang.menu.scanf.default.avr_scanf_flags=
atmegang.menu.scanf.full=Full scanf
atmegang.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
atmegang.menu.scanf.minimal=Minimal scanf
atmegang.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
atmegang.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
robotControl.menu.printf.default=Default printf
robotControl.menu.printf.default.avr_printf_flags=
robotControl.menu.printf.full=Full printf
robotControl.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
robotControl.menu.printf.minimal=Minimal printf
robotControl.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
robotControl.menu.scanf.default=Default scanf
robotControl.menu.scanf.default.avr_scanf_flags=
robotControl.menu.scanf.full=Full scanf
robotControl.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
robotControl.menu.scanf.minimal=Minimal scanf
robotControl.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
robotControl.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
robotMotor.menu.printf.default=Default printf
robotMotor.menu.printf.default.avr_printf_flags=
robotMotor.menu.printf.full=Full printf
robotMotor.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
robotMotor.menu.printf.minimal=Minimal printf
robotMotor.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
robotMotor.menu.scanf.default=Default scanf
robotMotor.menu.scanf.default.avr_scanf_flags=
robotMotor.menu.scanf.full=Full scanf
robotMotor.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
robotMotor.menu.scanf.minimal=Minimal scanf
robotMotor.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
robotMotor.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
gemma.menu.printf.default=Default printf
gemma.menu.printf.default.avr_printf_flags=
gemma.menu.printf.full=Full printf
gemma.menu.printf.full.avr_printf_flags=-Wl,-u,vfprintf -lprintf_flt
gemma.menu.printf.minimal=Minimal printf
gemma.menu.printf.minimal.avr_printf_flags=-Wl,-u,vfprintf -lprintf_min
gemma.menu.scanf.default=Default scanf
gemma.menu.scanf.default.avr_scanf_flags=
gemma.menu.scanf.full=Full scanf
gemma.menu.scanf.full.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_flt
gemma.menu.scanf.minimal=Minimal scanf
gemma.menu.scanf.minimal.avr_scanf_flags=-Wl,-u,vfscanf -lscanf_min
gemma.compiler.c.elf.extra_flags={avr_printf_flags} {avr_scanf_flags}
##############################################################
Update 2:
I found what appears to be the solution & posted it as my own answer, but I'm going to hold off for a day or two to test it thoroughly and make sure it actually works.