Activate SSE2 for all Visual Studio builds

BUG=
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/424763002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22675 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

build/toolchain.gypi

@@ -452,6 +452,12 @@
           'IntermediateDirectory': '$(OutDir)\\obj\\$(ProjectName)',
           'CharacterSet': '1',
         },
+        'msvs_settings': {
+          'VCCLCompilerTool': {
+            # Ensure no surprising artifacts from 80bit double math with x86.
+            'AdditionalOptions': ['/arch:SSE2'],
+          },
+        },
       }],
       ['OS=="win" and v8_enable_prof==1', {
         'msvs_settings': {