LF line endings for scripts that may need them

This fixes how init-tests-after-clone.sh appears in .gitattributes
so it gets LF (Unix-style) line endings on all systems as intended,
and adds Makefile to be treated the same way.

Author: EliahKagan

.gitattributes

@@ -1,2 +1,3 @@
 test/fixtures/* eol=lf
-init-tests-after-clone.sh
+init-tests-after-clone.sh eol=lf
+Makefile eol=lf