[PowerPC64] Use ld.bfd to build LIB32 and STAND - when using llvm

Summary:
This patch is to support ongoing work for replacing "GCC/BFD" by "CLANG/LLD" on
target PowerPC64 [1], by proposing a way to specify and/or locate a secondary
ld.bfd linker.
This is necessary as LLD currently doesn't support PowerPC 32 bits, so we keep
using BFD for the 32 bit stuff on PowePC64(LIB32 compatibility and
STAND/slof/loader.)

- creates LD_BFD variable pointing to ld.bfd
- use LD_BFD as linker for LIB32/compat
- Default behavior for other platforms aren't changed.

[1] https://wiki.freebsd.org/powerpc/llvm-elfv2

Submitted by:	alfredo.junior_eldorado.org.br
Reviewed by:	imp
Differential Revision: https://reviews.freebsd.org/D20261

share/mk/bsd.compat.mk

@@ -47,11 +47,20 @@ LIB32CPUFLAGS=	-mcpu=powerpc
 .else
 LIB32CPUFLAGS=	-mcpu=${COMPAT_CPUTYPE}
 .endif
+
+.if ${COMPAT_COMPILER_TYPE} == "gcc"
 LIB32CPUFLAGS+=	-m32
+.else
+LIB32CPUFLAGS+=	-target powerpc-unknown-freebsd13.0
+
+# Use BFD to workaround ld.lld issues on PowerPC 32 bit 
+LIB32CPUFLAGS+= -fuse-ld=${LD_BFD}
+.endif
+
 LIB32_MACHINE=	powerpc
 LIB32_MACHINE_ARCH=	powerpc
 LIB32WMAKEFLAGS=	\
-		LD="${XLD} -m elf32ppc_fbsd"
+		LD="${LD_BFD} -m elf32ppc_fbsd"
 
 .elif ${COMPAT_ARCH:Mmips64*} != ""
 HAS_COMPAT=32

share/mk/bsd.cpu.mk

@@ -412,3 +412,17 @@ CFLAGS_NO_SIMD += ${CFLAGS_NO_SIMD.${COMPILER_TYPE}}
 # These come from make.conf or the command line or the environment.
 CFLAGS += ${CFLAGS.${MACHINE_ARCH}}
 CXXFLAGS += ${CXXFLAGS.${MACHINE_ARCH}}
+
+
+# Defines a variable for Binutils linker, to be used to workaround some
+# issue with LLVM LLD (i.e. support for PowerPC32 bit on PowerPC64)
+#
+# This is an unavoidable cross coupling with Makefile.inc1 and
+# normal builds works when CROSS_BINUTILS_PREFIX and could be removed
+# when LLD PowerPC 32 bit support is completed
+.if defined(CROSS_BINUTILS_PREFIX)
+LD_BFD=${LOCALBASE}/bin/${CROSS_BINUTILS_PREFIX}-ld.bfd
+.else
+LD_BFD=${OBJTOP}/tmp/usr/bin/ld.bfd
+.endif
+

stand/defs.mk

@@ -99,6 +99,10 @@ CFLAGS+= -DLOADER_DISK_SUPPORT
 # or powerpc64.
 .if ${MACHINE_ARCH} == "powerpc64"
 CFLAGS+=	-m32 -mcpu=powerpc
+# Use ld.bfd to workaround ld.lld issues on PowerPC 32 bit
+.if "${COMPILER_TYPE}" == "clang" && "${LINKER_TYPE}" == "lld"
+CFLAGS+=	-fuse-ld=${LD_BFD}
+.endif
 .endif
 
 # For amd64, there's a bit of mixed bag. Some of the tree (i386, lib*32) is