stand: Use -Oz/-Os for all loader/stand builds.

While we're not super size constrained, the x86 BIOS /boot/loader has
to be less than about 520k-530k to be reliable. The LUA loader is at
this size today. -Oz saves 15-20% on the size, keeping us safely small
enough (comparable to where we were with the 4th loader). This will
also help with sjg's work on bringing in bearssl, though we may again
be looking for space in the LUA loader.

Size table for clang 6.0.0:
	default		-O1		-Os		-Oz
4th	442368		417792		389120		376832
lua	524288		479232		446464		430080

Tested by: kevans91@ (ubldr on armv7), dhw@ (loader on amdy64)
Differential Revision: https://reviews.freebsd.org/D16724

1 files changed, 6 insertions, 1 deletions

diff --git a/stand/defs.mk b/stand/defs.mk
index 2f8d97ae0f2c..e446fd0f6c94 100644
--- a/stand/defs.mk
+++ b/stand/defs.mk
@@ -53,7 +53,12 @@ CFLAGS+=	-I${SASRC} -D_STANDALONE
 CFLAGS+=	-I${SYSDIR}
 # Spike the floating point interfaces
 CFLAGS+=	-Ddouble=jagged-little-pill -Dfloat=floaty-mcfloatface
-
+# Slim down the image. This saves about 15% in size with clang 6 on x86
+# Our most constrained /boot/loader env is BIOS booting on x86, where
+# our text + data + BTX have to fit into 640k below the ISA hole.
+# Experience has shown that problems arise between ~520k to ~530k.
+CFLAGS.clang+=	-Oz
+CFLAGS.gcc+=	-Os
 
 # GELI Support, with backward compat hooks (mostly)
 .if defined(LOADER_NO_GELI_SUPPORT)