arch/x86/Makefile.inc: Pass $(AS) and $(CPP) to SeaBIOS

SeaBIOS’ Makefile requires cpp (C Preprocessor) to build. Modify
the xcompile script to search for cpp program path, and pass it to
SeaBIOS’ `Makefile.inc`. Also pass the program path for as (GNU assembler).

This is needed, so the crossgcc toolchain to build the SeaBIOS payload
under Mac OSX. OSX ships a cpp program, but it works differently
from GNU CPP, so we need to override it.

Change-Id: If996ffbb76ec4bd16079b54b41f3fac07bfe25be
Signed-off-by: Andrew Wu <arw@dmp.com.tw>
Reviewed-on: http://review.coreboot.org/3896
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Jonathan A. Kollasch <jakllsch@kollasch.net>

Makefile

@@ -126,6 +126,7 @@ ARCH-$(CONFIG_ARCH_X86)     := i386
 ifneq ($(INNER_SCANBUILD),y)
 CC := $(CC_$(ARCH-y))
 endif
+CPP := $(CPP_$(ARCH-y))
 AS := $(AS_$(ARCH-y))
 LD := $(LD_$(ARCH-y))
 NM := $(NM_$(ARCH-y))

src/arch/x86/Makefile.inc

@@ -427,6 +427,7 @@ seabios:
 			HOSTCC="$(HOSTCC)" \
 			CC="$(CC)" LD="$(LD)" OBJDUMP="$(OBJDUMP)" \
 			OBJCOPY="$(OBJCOPY)" STRIP="$(STRIP)" \
+			AS="$(AS)" CPP="$(CPP)" \
 			CONFIG_SEABIOS_MASTER=$(CONFIG_SEABIOS_MASTER) \
 			CONFIG_SEABIOS_STABLE=$(CONFIG_SEABIOS_STABLE) \
 			OUT=$(abspath $(obj)) IASL="$(IASL)"

util/xcompile/xcompile

@@ -117,6 +117,7 @@ report_arch_toolchain() {
 	cat <<EOF
 # elf${TWIDTH}-${TBFDARCH} toolchain (${GCCPREFIX}gcc)
 CC_${TARCH}:=${GCCPREFIX}gcc ${CFLAGS}
+CPP_${TARCH}:=${GCCPREFIX}cpp
 AS_${TARCH}:=${GCCPREFIX}as ${ASFLAGS}
 LD_${TARCH}:=${GCCPREFIX}ld${LINKER_SUFFIX} ${LDFLAGS}
 NM_${TARCH}:=${GCCPREFIX}nm