I needed this change to get "make install DESTDIR=..." to work here:
diff --git a/gitk-git/Makefile b/gitk-git/Makefile
index e1b6045..3021be0 100644
--- a/gitk-git/Makefile
+++ b/gitk-git/Makefile
@@ -40,6 +40,7 @@ endif
all:: gitk-wish $(ALL_MSGFILES)
install:: all
+ $(INSTALL) -d -m 755 '$(DESTDIR_SQ)$(bindir_SQ)'
$(INSTALL) -m 755 gitk-wish '$(DESTDIR_SQ)$(bindir_SQ)'/gitk
$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$(msgsdir_SQ)'
$(foreach p,$(ALL_MSGFILES), $(INSTALL) -m 644
$p '$(DESTDIR_SQ)$(msgsdir_SQ)' &&) true
Andreas