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, 4 insertions, 5 deletions

diff --git a/sys/boot/i386/gptboot/Makefile b/sys/boot/i386/gptboot/Makefile
index 48a6d59..e1a640a 100644
--- a/sys/boot/i386/gptboot/Makefile
+++ b/sys/boot/i386/gptboot/Makefile
@@ -36,11 +36,6 @@ CFLAGS=	-DBOOTPROG=\"gptboot\" \
 	-Wpointer-arith -Wshadow -Wstrict-prototypes -Wwrite-strings \
 	-Winline --param max-inline-insns-single=100
 
-.if ${CC:T:Mclang} == "clang"
-# XXX: clang integrated-as doesn't grok .codeNN directives yet
-CFLAGS+=	${.IMPSRC:T:Mgptldr.S:C/^.+$/-no-integrated-as/}
-.endif
-
 LDFLAGS=-static -N --gc-sections
 
 # Pick up ../Makefile.inc early.
@@ -79,3 +74,7 @@ machine:
 .endif
 
 .include <bsd.prog.mk>
+
+# XXX: clang integrated-as doesn't grok .codeNN directives yet
+CFLAGS.gptldr.S=	${CLANG_NO_IAS}
+CFLAGS+=		${CFLAGS.${.IMPSRC:T}}