Merge pull request #4429 from RaananW/gulp-fix-win

fixing npm install for windows

Tools/Gulp/package.json

@@ -62,7 +62,7 @@
         "webpack-stream": "^4.0.1"
     },
     "scripts": {
-        "install": "npm --prefix ../../Playground/ install ../../Playground/ && npm --prefix ../../tests/unit/ install ../../tests/unit/ && npm --prefix ../../Viewer/tests/ install ../../Viewer/tests/ && npm --prefix ../../Viewer/ install ../../Viewer/ && gulp deployLocalDev"
+        "install": "npm --prefix ../../Playground/ install ../../Playground/ && npm --prefix ../../tests/unit/ install ../../tests/unit/ && npm --prefix ../../Viewer/tests/ install ../../Viewer/tests/ && cd ../../Viewer && npm install && cd ../Tools/Gulp/ && gulp deployLocalDev"
     },
     "dependencies": {
         "dts-bundle": "^0.7.3",