Your filesystem may support hardlinks, but you may choose not to use them
when installing git-foo builtins and favor symblic links or copies for
whatever reason.

The installation procedure of git-gui/ directory is not touched with this
patch and git-citool still ends up being a hardlink to git-gui, but it
needs to be addressed separately.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>