if `uname -r` contains a '-g' in it, the check target fails

http://bugs.gentoo.org/159162
https://bugzilla.netfilter.org/bugzilla/show_bug.cgi?id=527

--- Makefile
+++ Makefile
@@ -249,7 +249,7 @@ distrib: check distclean delrelease $(RE
 # -g -pg -DIPTC_DEBUG
 .PHONY: check
 check:
-	@if echo $(CFLAGS) | egrep -e '-g|-pg|IPTC_DEBUG' >/dev/null; then echo Remove debugging flags; exit 1; else exit 0; fi
+	@if echo $(CFLAGS) | egrep -e '(^|[[:space:]])(-g|-pg|-DIPTC_DEBUG)([[:space:]]|$)' >/dev/null; then echo Remove debugging flags; exit 1; else exit 0; fi
 
 .PHONY: nowhitespace
 nowhitespace: