[gpm] [patch] fix DESTDIR usage

[Mike Frysinger]

Makefile.include.in utilizes DESTDIR, but it currently doesnt do anything with 
it :)

here's a small change where the behavior is to set ROOT equal to DESTDIR only 
if the user hasnt specified ROOT via cmdline

--- Makefile.include.in
+++ Makefile.include.in
@@ -7,3 +7,5 @@
 ROOT =
-DESTDIR = $(ROOT)
+ifndef ROOT
+ROOT = $(DESTDIR)
+endif

-mike