Define several extra macros in bsd.sys.mk and sys/conf/kern.pre.mk, to

get rid of testing explicitly for clang (using ${CC:T:Mclang}) in
individual Makefiles.

Instead, use the following extra macros, for use with clang:
- NO_WERROR.clang       (disables -Werror)
- NO_WCAST_ALIGN.clang  (disables -Wcast-align)
- NO_WFORMAT.clang	(disables -Wformat and friends)
- CLANG_NO_IAS		(disables integrated assembler)
- CLANG_OPT_SMALL	(adds flags for extra small size optimizations)

As a side effect, this enables setting CC/CXX/CPP in src.conf instead of
make.conf!  For clang, use the following:

CC=clang
CXX=clang++
CPP=clang-cpp

MFC after:	2 weeks

1 files changed, 6 insertions, 10 deletions

diff --git a/sys/boot/i386/boot2/Makefile b/sys/boot/i386/boot2/Makefile
index e2fc534..68e49ed 100644
--- a/sys/boot/i386/boot2/Makefile
+++ b/sys/boot/i386/boot2/Makefile
@@ -40,14 +40,8 @@ CFLAGS=	-Os \
 	-Wall -Waggregate-return -Wbad-function-cast -Wcast-align \
 	-Wmissing-declarations -Wmissing-prototypes -Wnested-externs \
 	-Wpointer-arith -Wshadow -Wstrict-prototypes -Wwrite-strings \
-	-Winline --param max-inline-insns-single=100
-
-.if ${CC:T:Mclang} == "clang"
-CFLAGS+=	-mllvm -stack-alignment=8 -mllvm -inline-threshold=3 \
-		-mllvm -enable-load-pre=false
-# XXX: clang integrated-as doesn't grok .codeNN directives yet
-CFLAGS+=	${.IMPSRC:T:Mboot1.S:C/^.+$/-no-integrated-as/}
-.endif
+	-Winline --param max-inline-insns-single=100 \
+	${CLANG_OPT_SMALL}
 
 LDFLAGS=-static -N --gc-sections
 
@@ -89,9 +83,7 @@ boot2.out: ${BTXCRT} boot2.o sio.o
 	${LD} ${LDFLAGS} -Ttext ${ORG2} -o ${.TARGET} ${.ALLSRC}
 
 boot2.o: boot2.s
-.if ${CC:T:Mclang} == "clang"
 	${CC} ${ACFLAGS} -c boot2.s
-.endif
 
 SRCS=	boot2.c boot2.h
 
@@ -115,3 +107,7 @@ machine:
 .endif
 
 .include <bsd.prog.mk>
+
+# XXX: clang integrated-as doesn't grok .codeNN directives yet
+CFLAGS.boot1.S=		${CLANG_NO_IAS}
+CFLAGS+=		${CFLAGS.${.IMPSRC:T}}