git-gui: Honor TCLTK_PATH if supplied
git-gui: Honor TCLTK_PATH if supplied

Mimick what we do for gitk.  Since you do have a source file,
git-gui.sh, which is separate from the target, it should be much
easier in git-gui's Makefile.

Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>
Signed-off-by: Shawn O. Pearce <f01032651c12a22b2103346ba96b3b6b231f9d3c@spearce.org>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git