Makefile.d/arch_test.h: Add detection for ARC64 architecture

Change-Id: I8707394871994f600b345d76614c5689fd081db4
Signed-off-by: Veronika Kremneva <kremneva@synopsys.com>
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/63896
Original-Reviewed-by: Thomas Heijligen <src@posteo.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/72343
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/Makefile.d/arch_test.h b/Makefile.d/arch_test.h
index 99f84d0..04aa121 100644
--- a/Makefile.d/arch_test.h
+++ b/Makefile.d/arch_test.h
@@ -45,6 +45,8 @@
 	#define __FLASHROM_ARCH__ "s390"
 #elif defined(__arc__)
 	#define __FLASHROM_ARCH__ "arc"
+#elif defined(__ARC64__)
+	#define __FLASHROM_ARCH__ "arc64"
 #elif defined(__e2k__)
 	#define __FLASHROM_ARCH__ "e2k"
 #else