Makefile: make hard/symbolic links for non-builtins too

Makefile: make hard/symbolic links for non-builtins too

To conserve space/improve file caching we try to make hard or symbolic links
from each builtin program to the main git executable rather than having
each be a complete duplicate copy of it.  We weren't doing this for the
non-builtin programs though.  So, just because we can, and because it's
easy, and for completeness sake, let's do it.

Signed-off-by: Brandon Casey <redacted>
Reviewed-by: Jonathan Nieder <redacted>
Signed-off-by: Junio C Hamano <redacted>