Symlink pg_replslot robustly on Windows in pg_basebackup test

This reverts commit e9f15bc. Instead of a hacky solution that didn't
work on Windows, we avoid trying to move the directory possibly across
drives, and instead remove it and recreate it in the new location.

Discussion: https://postgr.es/m/20240707070243.sb77kp4ubowauctz@awork3.anarazel.de

Backpatch to release 14 like the previous patch.

Author: adunstan

src/bin/pg_basebackup/t/010_pg_basebackup.pl

@@ -359,13 +359,13 @@
 # Create a temporary directory in the system location.
 my $sys_tempdir = PostgreSQL::Test::Utils::tempdir_short;
 
-# On Windows use the short location to avoid path length issues.
-# Elsewhere use $tempdir to avoid file system boundary issues with moving.
-my $tmploc = $windows_os ? $sys_tempdir : $tempdir;
-
-rename("$pgdata/pg_replslot", "$tmploc/pg_replslot")
-  or BAIL_OUT "could not move $pgdata/pg_replslot";
-dir_symlink("$tmploc/pg_replslot", "$pgdata/pg_replslot")
+# pg_replslot should be empty. We remove it and recreate it in $sys_tempdir
+# before symlinking, in order to avoid possibly trying to move things across
+# drives.
+rmdir("$pgdata/pg_replslot")
+  or BAIL_OUT "could not remove $pgdata/pg_replslot";
+mkdir("$sys_tempdir/pg_replslot"); # if this fails the symlink will fail
+dir_symlink("$sys_tempdir/pg_replslot", "$pgdata/pg_replslot")
   or BAIL_OUT "could not symlink to $pgdata/pg_replslot";
 
 $node->start;