build system: remove duplicate architecture list

Let xcompile pass the list of architectures, given
that it already has it.

Change-Id: I565512d3bef987c9a4e48a39bfd88bacf0b65de9
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/6254
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Marc Jones <marc.jones@se-eng.com>

toolchain.inc

@@ -17,8 +17,6 @@
 ## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 ##
 
-ARCH_SUPPORTED := armv7 x86_32
-
 # ccache integration
 ifeq ($(CONFIG_CCACHE),y)
 

util/xcompile/xcompile

@@ -145,6 +145,7 @@ detect_special_flags() {
 report_arch_toolchain() {
 	cat <<EOF
 # elf${TWIDTH}-${TBFDARCH} toolchain (${GCCPREFIX}gcc)
+ARCH_SUPPORTED+=${TARCH}
 CC_${TARCH}:=${GCCPREFIX}gcc
 CFLAGS_${TARCH}:=${CFLAGS}
 CPP_${TARCH}:=${GCCPREFIX}cpp