Gentoo Bug: https://bugs.gentoo.org/show_bug.cgi?id=542676

https://svnweb.freebsd.org/base/head/sys/boot/i386/boot2/Makefile?r1=272249&r2=276479

diff --git a/sys/boot/i386/boot2/Makefile b/sys/boot/i386/boot2/Makefile
index 8a6e771..c030853 100644
--- a/sys/boot/i386/boot2/Makefile
+++ b/sys/boot/i386/boot2/Makefile
@@ -22,8 +22,7 @@ BOOT2_UFS?=	UFS1_AND_UFS2
 #BOOT2_UFS?=	UFS2_ONLY
 #BOOT2_UFS?=	UFS1_ONLY
 
-CFLAGS=	-Os \
-	-fomit-frame-pointer \
+CFLAGS= -fomit-frame-pointer \
 	-mrtd \
 	-mregparm=3 \
 	-DUSE_XREAD \
@@ -40,7 +39,10 @@ CFLAGS=	-Os \
 	-Winline \
 	${CLANG_OPT_SMALL}
 
-CFLAGS.gcc+=	-fno-guess-branch-probability \
+CFLAGS.clang+=	-Oz
+
+CFLAGS.gcc+=	-Os \
+		-fno-guess-branch-probability \
 		-fno-unit-at-a-time \
 		--param max-inline-insns-single=100
 .if ${COMPILER_TYPE} == "gcc" && ${COMPILER_VERSION} <= 40201