explicitly pass `%PLATFORM%` to `scripts/build_for_node_webkit.cmd`

appveyor.yml

@@ -30,7 +30,7 @@ install:
   # make commit message env var shorter
   - SET CM=%APPVEYOR_REPO_COMMIT_MESSAGE%
   - if not "%CM%" == "%CM:[publish binary]=%" node-pre-gyp --msvs_version=2013 publish
-  - call scripts\build_for_node_webkit.cmd
+  - call scripts\build_for_node_webkit.cmd %PLATFORM%
 
 build: OFF
 test: OFF

scripts/build_for_node_webkit.cmd

 set
-if not "%PLATFORM%" == "x86" goto end
+if not "%1" == "x86" goto end
 if "%nw_version%" == "" goto end
 node-pre-gyp clean
 npm install nw-gyp