Add missing changes from ARCH removal.

I somehow didn't upload these fixes from the review. So doing that
now.

Test: Unit tests pass.
Change-Id: Ia17e480eb972db4f7be6947c0e6567632c65431f
diff --git a/scripts/stack b/scripts/stack
index 2e83ff2..713bbc3 100755
--- a/scripts/stack
+++ b/scripts/stack
@@ -44,10 +44,7 @@
 
   args = parser.parse_args()
   if args.arch:
-    if args.arch == "arm" or args.arch == "x86":
-      symbol.ARCH_IS_32BIT = True
-    else:
-      symbol.ARCH_IS_32BIT = False
+    symbol.ARCH_IS_32BIT = not "64" in args.arch
   if args.symbols_dir:
     symbol.SYMBOLS_DIR = args.symbols_dir
   if args.symbols_zip: