Addresses issue where build script doesn't terminate automatically as expected.

Author: nhobi

packages/react-scripts/scripts/build.js

@@ -102,6 +102,8 @@ measureFileSizesBeforeBuild(paths.appBuild)
         buildFolder,
         useYarn
       );
+      
+      process.exit();
     },
     err => {
       console.log(chalk.red('Failed to compile.\n'));