--- zgv-5.9/config.mk.orig	2007-07-30 08:51:55.859285387 +0700
+++ zgv-5.9/config.mk	2007-07-30 08:52:44.113938239 +0700
@@ -7,8 +7,8 @@
 # Set the C compiler to use, and options for it.
 # This is likely to be what you'll want for most systems:
 #
-CC=gcc
-CFLAGS=-O2 -Wall -fomit-frame-pointer -finline-functions
+CC?=gcc
+CFLAGS?=-O2 -Wall -fomit-frame-pointer -finline-functions
 #
 # If you're brave enough to try compiling zgv on a non-x86 system :-),
 # this might be a better bet:
@@ -20,13 +20,13 @@
 # (This should be a `new' awk, such as gawk or mawk.) This setting
 # should work for Linux and *BSD.
 #
-AWK=awk
+AWK?=awk
 
 # Set display backend to use. svgalib is the `native' one and
 # is likely to remain preferable. The SDL backend is now quite
 # usable, but tends to be rather slower.
 #
-BACKEND=SVGALIB
+BACKEND?=SVGALIB
 #BACKEND=SDL
 
 
@@ -37,7 +37,7 @@
 # MANDIR to directory for man page.
 # Usually it will be simpler to just set PREFIX.
 #
-PREFIX=/usr/local
+PREFIX?=/usr/local
 
 # In theory it would be nice to put the info file and man page under
 # /usr/local/share. However, it's not clear if this is widely
@@ -59,7 +59,7 @@
 # Set the location/filename of the system-wide configuration file. You
 # may prefer to have this under /etc, for example.
 #
-RCFILE=$(PREFIX)/etc/zgv.conf
+RCFILE?=$(PREFIX)/etc/zgv.conf
 
 
 # Normally `make install' will update your `dir' file (in INFODIR),
@@ -91,7 +91,7 @@
 # colours will be recognised, which will mean many XPMs won't be
 # readable. This setting should be ok.
 #
-RGB_DB=/usr/X11R6/lib/X11/rgb.txt
+RGB_DB?=/usr/X11R6/lib/X11/rgb.txt
 
 # Finally, an option for `make dvi' in the `doc' directory. You only need
 # worry about what this is set to if you plan to make a printed manual.
@@ -102,4 +102,4 @@
 # edit this file when you do `make dvi', but that's only because
 # doc/Makefile isn't as smart about that as it should be. :-))
 #
-USE_A4_DEF=-t @afourpaper
+USE_A4_DEF?=-t @afourpaper