[build] Port options to support win-clang

build/standalone.gypi

Index: build/standalone.gypi
diff --git a/build/standalone.gypi b/build/standalone.gypi
index eccf2f49fb0d168a476062487a55241e9240e190..a7572c3e1093c4819b976aa037bca1c53daae52b 100644
--- a/build/standalone.gypi
+++ b/build/standalone.gypi
@@ -946,6 +946,31 @@
               }],
             ],
           },
+          'conditions': [
+            ['clang==1', {
+              'VCCLCompilerTool': {
+                'AdditionalOptions': [
+                  # Don't warn about unused function parameters.
+                  # (This is also used on other platforms.)
+                  '-Wno-unused-parameter',
+                  # Don't warn about the "struct foo f = {0};" initialization
+                  # pattern.
+                  '-Wno-missing-field-initializers',
+
+                  # Many files use intrinsics without including this header.
+                  # TODO(hans): Fix those files, or move this to sub-GYPs.
+                  '/FIIntrin.h',
+
+                  # TODO(hans): Make this list shorter eventually, http://crbug.com/504657
+                  '-Wno-microsoft-enum-value',  # http://crbug.com/505296
+                  '-Wno-unknown-pragmas',  # http://crbug.com/505314
+                  '-Wno-microsoft-cast',  # http://crbug.com/550065
+
+                  '-fmsc-version=1900',

[Nico, 2016/04/14 13:54:12]

1900 means msvc2015. If you're still on 2013, you might want 1800 here

[Michael Achenbach, 2016/04/14 14:03:42]

Yea - but no point in supporting also 2013 with clang as we never supported
win-clang...

[Nico, 2016/04/14 14:48:06]

In general, I feel you'll have fewest problems if the version here matches the
versions of the MSVC headers you're using. If you're using the 2015 headers,
this _must_ be 1900 since clang-cl in 2013 mode can't parse the 2015 headers. If
you're using clang-cl in 2015 mode with the 2013 headers, then that might work,
but you're using a configuration that as far as I know nobody else uses.

+                ],
+              },
+            }],
+          ],
         },
       },
     }],  # OS=="win"