Build only the appropriate x86 arches for nacl (chrome side).

build/common_untrusted.gypi

Index: build/common_untrusted.gypi
diff --git a/build/common_untrusted.gypi b/build/common_untrusted.gypi
index 086264e032771a26e8771a17ff7487982a633b3e..bcc368646bce021fad55a20d5594cb5a993bdda2 100644
--- a/build/common_untrusted.gypi
+++ b/build/common_untrusted.gypi
@@ -10,6 +10,17 @@
   ],
   'target_defaults': {
     'conditions': [
+      # TODO(bradnelson): Drop this once the nacl side does the same.
+      ['target_arch=="x64"', {
+        'variables': {
+          'enable_x86_32': 0,
+        },
+      }],
+      ['target_arch=="ia32" and OS!="win"', {
+        'variables': {
+          'enable_x86_64': 0,
+        },
+      }],
       ['target_arch=="arm"', {
         'variables': {
           'clang': 1,
@@ -26,4 +37,4 @@
       }],
     ],
   },
-}
+}