MFP4 222356, 222371, 222375, 222391, 222403, 222407, 222411

Add support for an external cross compiler.  The cross compiler is
specified by passing the XCC, XCXX, and XCPP variables (corresponding to
CC, CXX, and CPP) to buildworld/buildkernel.  The compiler must be clang
or be configured to target the appropriate architecture.

To speed build times, if XCC is an absolute path or
WITHOUT_CROSS_COMPILER is defined then no cross compiler will be built
during the cross-tools stage.

To facilitate the use of unmodified external compilers, a
WITHOUT_FORMAT_EXTENSIONS option is available to supress printf format
checking.

As a short-term measure, supress a few new clang warnings during kernel
builds.

Sponsored by:	DARPA, AFRL
Reviewed by:	xxx

--- ../../freebsd/src/Makefile.inc1	2013-02-26 21:31:09.000000000 +0000
+++ ./Makefile.inc1	2013-02-27 23:31:46.000000000 +0000
@@ -280,15 +280,61 @@
 .if ${MK_CDDL} == "no"
 WMAKEENV+=	NO_CTF=1
 .endif
-.if ${CC:T:Mgcc} == "gcc"
+
+.if defined(CROSS_TOOLCHAIN_PATH)
+CROSS_COMPILER_PATH?=${CROSS_TOOLCHAIN_PATH}
+CROSS_BINUTILS_PATH?=${CROSS_TOOLCHAIN_PATH}
+.endif
+XCOMPILERS=	CC CXX CPP
+.for COMPILER in ${XCOMPILERS}
+.if defined(CROSS_COMPILER_PATH)
+X${COMPILER}?=	${CROSS_COMPILER_PATH}/${${COMPILER}}
+.else
+X${COMPILER}?=	${${COMPILER}}
+.endif
+.endfor
+XBINUTILS=	AS AR LD NM OBJDUMP RANLIB STRINGS
+.for BINUTIL in ${XBINUTILS}
+.if defined(CROSS_BINUTILS_PATH)
+X${BINUTIL}?=	${CROSS_BINUTILS_PATH}/${${BINUTIL}}
+.else
+X${BINUTIL}?=	${${BINUTIL}}
+.endif
+.endfor
+WMAKEENV+=	CC="${XCC} ${XFLAGS}" CXX="${XCXX} ${XFLAGS}" \
+		CPP="${XCPP} ${XFLAGS}" \
+		AS="${XAS}" AR="${XAR}" LD="${XLD}" NM=${XNM} \
+		OBJDUMP=${XOBJDUMP} RANLIB=${RANLIB} STRINGS=${XSTRINGS}
+
+.if ${XCC:T:Mgcc} == "gcc"
 WMAKE_COMPILER_TYPE=	gcc
-.elif ${CC:T:Mclang} == "clang"
+.elif ${XCC:T:Mclang} == "clang"
 WMAKE_COMPILER_TYPE=	clang
 .elif ${MK_CLANG_IS_CC} == "no"
 WMAKE_COMPILER_TYPE=	gcc
 .else
 WMAKE_COMPILER_TYPE=	clang
 .endif
+
+.if ${XCC:M/*}
+XFLAGS=		--sysroot=${WORLDTMP}
+.if defined(CROSS_BINUTILS_PATH)
+XFLAGS+=	-B${CROSS_BINUTILS_PATH}
+.else
+XFLAGS+=	-B${WORLDTMP}/usr/bin
+.endif
+.if ${TARGET_ARCH} != ${MACHINE_ARCH} && ${WMAKE_COMPILER_TYPE} == "clang"
+.if (${TARGET_ARCH} == "arm" || ${TARGET_ARCH} == "armv6") && \
+${MK_ARM_EABI} != "no"
+TARGET_ABI=	gnueabi
+.else
+TARGET_ABI=	unknown
+.endif
+TARGET_TRIPLE?=	${TARGET_ARCH:C/amd64/x86_64/}-${TARGET_ABI}-freebsd10.0
+XFLAGS+=	-target ${TARGET_TRIPLE}
+.endif
+.endif
+
 WMAKEENV+=	COMPILER_TYPE=${WMAKE_COMPILER_TYPE}
 WMAKE=		${WMAKEENV} ${MAKE} ${WORLD_FLAGS} -f Makefile.inc1 DESTDIR=${WORLDTMP}
 
@@ -321,6 +367,7 @@
 
 
 LIB32FLAGS=	-m32 ${LIB32CPUFLAGS} -DCOMPAT_32BIT \
+		--sysroot=${WORLDTMP} \
 		-isystem ${LIB32TMP}/usr/include/ \
 		-L${LIB32TMP}/usr/lib32 \
 		-B${LIB32TMP}/usr/lib32
@@ -336,8 +383,8 @@
 		SHLIBDIR=/usr/lib32 \
 		COMPILER_TYPE=${WMAKE_COMPILER_TYPE}
 LIB32WMAKEFLAGS+=	\
-		CC="${CC} ${LIB32FLAGS}" \
-		CXX="${CXX} ${LIB32FLAGS}" \
+		CC="${XCC} ${LIB32FLAGS}" \
+		CXX="${XCXX} ${LIB32FLAGS}" \
 		DESTDIR=${LIB32TMP} \
 		-DCOMPAT_32BIT \
 		-DLIBRARIES_ONLY \
@@ -1284,10 +1331,13 @@
 .endif
 .endif
 
-.if ${MK_BINUTILS} != "no"
+.if ${XAS:M/*} == "" && ${MK_BINUTILS} != "no"
 _binutils=	gnu/usr.bin/binutils
 .endif
 
+# If an full path to an external cross compiler is given, don't build
+# a cross compiler.
+.if ${XCC:M/*} == "" && ${MK_CROSS_COMPILER} != "no"
 .if ${MK_CLANG} != "no" && (${MK_CLANG_IS_CC} != "no" || ${CC:T:Mclang} == "clang")
 _clang=		usr.bin/clang
 _clang_libs=	lib/clang
@@ -1296,6 +1346,7 @@
 .if ${MK_GCC} != "no" && (${MK_CLANG_IS_CC} == "no" || ${TARGET} == "pc98")
 _cc=		gnu/usr.bin/cc
 .endif
+.endif
 
 cross-tools:
 .for _tool in \
--- ../../freebsd/src/share/mk/bsd.own.mk	2013-02-15 18:49:13.000000000 +0000
+++ share/mk/bsd.own.mk	2013-02-26 21:10:50.000000000 +0000
@@ -262,6 +262,7 @@
     CAPSICUM \
     CDDL \
     CPP \
+    CROSS_COMPILER \
     CRYPT \
     CTM \
     CVS \
@@ -271,6 +272,7 @@
     ED_CRYPTO \
     EXAMPLES \
     FLOPPY \
+    FORMAT_EXTENSIONS \
     FORTH \
     FP_LIBC \
     FREEBSD_UPDATE \
--- ../../freebsd/src/sys/conf/kern.mk	2012-11-11 22:15:16.000000000 +0000
+++ sys/conf/kern.mk	2013-02-26 20:35:48.000000000 +0000
@@ -5,7 +5,7 @@
 #
 CWARNFLAGS?=	-Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
 		-Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual \
-		-Wundef -Wno-pointer-sign -fformat-extensions \
+		-Wundef -Wno-pointer-sign ${FORMAT_EXTENTIONS} \
 		-Wmissing-include-dirs -fdiagnostics-show-option \
 		${CWARNEXTRA}
 #
@@ -29,7 +29,18 @@
 # enough to error out the whole kernel build.  Display them anyway, so there is
 # some incentive to fix them eventually.
 CWARNEXTRA?=	-Wno-error-tautological-compare -Wno-error-empty-body \
-		-Wno-error-parentheses-equality
+		-Wno-error-parentheses-equality \
+		-Wno-sizeof-pointer-memaccess \
+		-Wno-unused-command-line-argument \
+		${NO_WFORMAT}
+.endif
+
+# External compilers may not support our format extensions.  Allow them
+# to be disabled.  WARNING: format checking is disabled in this case.
+.if ${MK_FORMAT_EXTENSIONS} == "no"
+NO_WFORMAT=		-Wno-format
+.else
+FORMAT_EXTENTIONS=	-fformat-extensions
 .endif
 
 #
diff -uN ../../freebsd/src/tools/build/options/WITHOUT_CROSS_COMPILER tools/build/options/WITHOUT_CROSS_COMPILER
--- ../../freebsd/src/tools/build/options/WITHOUT_CROSS_COMPILER	1970-01-01 00:00:00.000000000 +0000
+++ tools/build/options/WITHOUT_CROSS_COMPILER	2013-02-26 21:10:50.000000000 +0000
@@ -0,0 +1,3 @@
+.\" $FreeBSD$
+Set to not build a cross compiler in the cross-tools stage of
+buildworld, buildkernel, etc.
diff -uN ../../freebsd/src/tools/build/options/WITHOUT_FORMAT_EXTENSIONS tools/build/options/WITHOUT_FORMAT_EXTENSIONS
--- ../../freebsd/src/tools/build/options/WITHOUT_FORMAT_EXTENSIONS	1970-01-01 00:00:00.000000000 +0000
+++ tools/build/options/WITHOUT_FORMAT_EXTENSIONS	2013-02-26 20:35:48.000000000 +0000
@@ -0,0 +1,5 @@
+.\" $FreeBSD$
+Set to not enable
+.Fl fformat-extensions
+when compiling the kernel.
+Also disables all format checking.