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

3 files changed, 6 insertions, 10 deletions

diff --git a/lib/libsm/Makefile b/lib/libsm/Makefile
index 661e87a..f2f19fb 100644
--- a/lib/libsm/Makefile
+++ b/lib/libsm/Makefile
@@ -18,12 +18,10 @@ CFLAGS+=${SENDMAIL_CFLAGS}
 
 WARNS?=	2
 
-.if ${CC:T:Mclang} == "clang"
 # Unfortunately, clang gives warnings about sendmail code that cannot
 # be turned off yet.  Since this is contrib code, and we don't really
 # care about the warnings, just make them non-fatal for now.
-NO_WERROR=
-.endif
+NO_WERROR.clang=
 
 LIB=	sm
 
diff --git a/lib/libthread_db/Makefile b/lib/libthread_db/Makefile
index a66f25d..b612f4f 100644
--- a/lib/libthread_db/Makefile
+++ b/lib/libthread_db/Makefile
@@ -16,10 +16,8 @@ SYM_MAPS+=${.CURDIR}/Symbol.map
 SYMBOL_MAPS=${SYM_MAPS}
 VERSION_DEF=${.CURDIR}/../libc/Versions.def
 
-.if ${CC:T:Mclang} == "clang"
 # Unfortunately, clang gives an incorrect warning about alignment in
 # arch/i386/libpthread_md.c, so turn that off for now.
-NO_WCAST_ALIGN=
-.endif
+NO_WCAST_ALIGN.clang=
 
 .include <bsd.lib.mk>
diff --git a/lib/libz/Makefile b/lib/libz/Makefile
index 8ae9aeb..e373e83 100644
--- a/lib/libz/Makefile
+++ b/lib/libz/Makefile
@@ -47,10 +47,6 @@ ACFLAGS+=	-Wa,--noexecstack
 #SRCS+=		gvmat64.S
 #CFLAGS+=	-DASMV -DNO_UNDERLINE
 #ACFLAGS+=	-Wa,--noexecstack
-#.if ${CC:T:Mclang} == "clang"
-## XXX: clang integrated-as doesn't grok .intel_syntax directives yet
-#ACFLAGS+=	${.IMPSRC:T:Mgvmat64.S:C/^.+$/-no-integrated-as/}
-#.endif
 #.endif
 
 VERSION_DEF=	${.CURDIR}/Versions.def
@@ -71,3 +67,7 @@ test: example minigzip
 		echo hello world | ./minigzip | ./minigzip -d )
 
 .include <bsd.lib.mk>
+
+## XXX: clang integrated-as doesn't grok .intel_syntax directives yet
+#ACFLAGS.gvmat64.S=	${CLANG_NO_IAS}
+#ACFLAGS+=		${ACFLAGS.${.IMPSRC:T}}