Disables Thread-Safe for local static variables.

Fixes sass#1283.

Author: am11

appveyor.yml

@@ -36,7 +36,8 @@
     - node --version
     - npm --version
     - git submodule update --init --recursive
-    - npm install --msvs_version=2015
+    - npm config set msvs_version 2015 --global
+    - npm install
 
   test_script: npm test
 
@@ -87,6 +88,7 @@
     - node --version
     - npm --version
     - git submodule update --init --recursive
-    - npm install --msvs_version=2015
+    - npm config set msvs_version 2015 --global
+    - npm install
 
   test_script: npm test

binding.gyp

@@ -64,6 +64,16 @@
             'MACOSX_DEPLOYMENT_TARGET': '10.7'
           }
         }],
+        ['OS=="win" and MSVS_VERSION == "2015"', {
+          'msvs_settings': {
+            'VCCLCompilerTool': {
+              'AdditionalOptions': [
+                # disable Thread-Safe "Magic" for local static variables
+                '/Zc:threadSafeInit-',
+              ],
+            },
+          },
+        }],
         ['OS!="win"', {
           'cflags_cc+': [
             '-std=c++0x'