Additional fix to service worker config for "homepage" field (#2262)

Author: gaearon

packages/react-scripts/config/webpack.config.prod.js

@@ -321,7 +321,7 @@ module.exports = {
       staticFileGlobsIgnorePatterns: [/\.map$/, /asset-manifest\.json$/],
       // Work around Windows path issue in SWPrecacheWebpackPlugin:
       // https://github.com/facebookincubator/create-react-app/issues/2235
-      stripPrefix: path.join(paths.appBuild).replace(/\\/g, '/'),
+      stripPrefix: paths.appBuild.replace(/\\/g, '/') + '/',
     }),
     // Moment.js is an extremely popular library that bundles large locale files
     // by default due to how Webpack interprets its code. This is a practical