Only build the x86 arches we actually need.

tools.gyp

Index: tools.gyp
diff --git a/tools.gyp b/tools.gyp
index d46051165a7be87670018a640ae05d2b036bacdf..bebeb9dff61edcaea62311c694299b12373e67d1 100644
--- a/tools.gyp
+++ b/tools.gyp
@@ -34,10 +34,14 @@
         'prep_nacl_sdk',
       ],
       'conditions': [
-        ['target_arch=="ia32" or target_arch=="x64"', {
+        ['target_arch=="ia32" or (target_arch=="x64" and OS=="win")', {
           'dependencies': [
             'crt_init_32',
             'crt_fini_32',
+          ],
+        }],
+        ['(target_arch=="ia32" and OS=="win") or target_arch=="x64"', {
+          'dependencies': [
             'crt_init_64',
             'crt_fini_64',
           ],
@@ -245,7 +249,7 @@
     },
   ],
   'conditions': [
-    ['target_arch=="ia32" or target_arch=="x64"', {
+    ['(target_arch=="ia32" and OS=="win") or target_arch=="x64"', {
       'targets' : [
         {
           'target_name': 'crt_init_64',
@@ -297,7 +301,7 @@
         }
       ],
     }],
-    ['target_arch=="ia32" or target_arch=="x64"', {
+    ['target_arch=="ia32" or (target_arch=="x64" and OS=="win")', {
       'targets' : [
         {
           'target_name': 'crt_init_32',