Skip "GRE" registration since that assumes write access to `/etc'.

--- icecat-3.0.1-g1/xulrunner/installer/Makefile.in	2008-07-27 12:52:16.000000000 +0200
+++ icecat-3.0.1-g1/xulrunner/installer/Makefile.in	2008-09-08 17:19:17.000000000 +0200
@@ -71,6 +71,7 @@ $(MOZILLA_VERSION).system.conf: $(topsrc
 	printf "[%s]\nGRE_PATH=%s\nxulrunner=true\nabi=%s" \
 	  $(MOZILLA_VERSION) $(installdir) $(TARGET_XPCOM_ABI)> $@
 
+SKIP_GRE_REGISTRATION = yes
 ifndef SKIP_GRE_REGISTRATION
 # to register xulrunner per-user, override this with $HOME/.gre.d
 regdir = /etc/gre.d