clang/win: Enable fastbuild=1 by default for now.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 32890147712570e1700dd8023eab30b0c01b05b5..4abef38936819137358067362ad6d39638fdc71e 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -2441,6 +2441,13 @@
         ],
       }],
 
+      ['OS=="win" and clang==1', {
+        # TODO(thakis): Remove this again once building with clang/win and
+        # debug info doesn't make link.exe run for hours.
+        'fastbuild': 1,
+      }],
+
+
       ['host_clang==1', {
         'host_cc': '<(make_clang_dir)/bin/clang',
         'host_cxx': '<(make_clang_dir)/bin/clang++',