crossgcc: Add RISC-V support

Change-Id: If1e0f7ed21f67d7a185dad251ede81ddbc18c4e5
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/8629
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
diff --git a/util/crossgcc/buildgcc b/util/crossgcc/buildgcc
index e9936db..8ddeea0 100755
--- a/util/crossgcc/buildgcc
+++ b/util/crossgcc/buildgcc
@@ -230,6 +230,7 @@
 	i386-elf)	;;
 	i386-mingw32)	;;
 	mipsel-elf)	;;
+	riscv-elf)	;;
 	i386*)		TARGETARCH=i386-elf;;
 	arm*)		TARGETARCH=armv7-a-eabi;;
 	aarch64*)	TARGETARCH=aarch64-elf;;