Index: lib/atf/libatf-c/Makefile
===================================================================
--- lib/atf/libatf-c/Makefile
+++ lib/atf/libatf-c/Makefile
@@ -28,9 +28,9 @@
 .include <src.opts.mk>
 .include <bsd.init.mk>
 
-_CFLAGS:=	${CFLAGS}
-_CPPFLAGS:=	${CPPFLAGS}
-_CXXFLAGS:=	${CXXFLAGS}
+_CFLAGS:=	${CFLAGS:M-[DILOWf]*}
+_CPPFLAGS:=	${CPPFLAGS:M-[DILOWf]*}
+_CXXFLAGS:=	${CXXFLAGS:M-[DILOWf]*}
 
 LIB=		atf-c
 PRIVATELIB=	true