Makefile: use /usr/ucb/install on SunOS platforms rather than ginstall

We can avoid a GNU dependency by using /usr/ucb/install.

Signed-off-by: Brandon Casey <drafnel@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -715,7 +715,7 @@ ifeq ($(uname_S),SunOS)
 		NO_C99_FORMAT = YesPlease
 		NO_STRTOUMAX = YesPlease
 	endif
-	INSTALL = ginstall
+	INSTALL = /usr/ucb/install
 	TAR = gtar
 	BASIC_CFLAGS += -D__EXTENSIONS__
 endif