libpayload: Add compiler switch

clang is totally untested, but it mirrors coreboot now.

Change-Id: I0e13ff8bba2007159a4a795ca07d187504b606b2
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: http://review.coreboot.org/10800
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

payloads/libpayload/Kconfig

@@ -55,6 +55,24 @@ config DEVELOPER
 	  Prompt for developer options. These options are only interesting for
 	  libpayload developers.
 
+choice
+	prompt "Compiler to use"
+	default COMPILER_GCC
+	help
+	  This option allows you to select the compiler.
+
+config COMPILER_GCC
+	bool "GCC"
+	help
+	  Use the GNU Compiler Collection (GCC).
+
+config COMPILER_LLVM_CLANG
+	bool "LLVM/clang"
+	help
+	  Use LLVM/clang.
+
+endchoice
+
 config REMOTEGDB
 	bool "Remote GDB stub"
 	default n

payloads/libpayload/util/xcompile/xcompile

@@ -182,7 +182,7 @@ report_arch_toolchain() {
 # elf${TWIDTH}-${TBFDARCH} toolchain (${GCC})
 ARCH_SUPPORTED+=${TARCH}
 SUBARCH_SUPPORTED+=${TSUPP-${TARCH}}
-ifeq (\$(CONFIG_COMPILER_GCC),y)
+ifeq (\$(CONFIG_LP_COMPILER_GCC),y)
 CC_${TARCH}:=${GCC}
 CFLAGS_${TARCH}:=${CFLAGS_GCC}
 COMPILER_RT_${TARCH}:=${CC_RT_GCC}