--- opennhrp-0.9.2/Makefile.orig	Tue Feb  3 14:51:18 2009
+++ opennhrp-0.9.2/Makefile	Tue Feb  3 14:51:07 2009
@@ -22,9 +22,9 @@
 INSTALL=install
 INSTALLDIR=$(INSTALL) -d
 
-CFLAGS=-Werror -Wall -Wstrict-prototypes -std=gnu99 -O2 \
-       -DOPENNHRP_VERSION=\"$(FULL_VERSION)\"
-LDFLAGS=
+CFLAGS?=-Werror -Wall -Wstrict-prototypes -O2
+CFLAGS+=-std=gnu99 -DOPENNHRP_VERSION=\"$(FULL_VERSION)\"
+LDFLAGS?=
 
 DESTDIR=
 SBINDIR=/usr/sbin