Propagate build process status

Build process is hiding away the status and doesn't propagate it to `fec build` status code, resulting in hiding away CI errors.

packages/config/src/bin/build-script.ts

@@ -26,6 +26,7 @@ export function buildScript(argv: { [name: string]: string }, cwd: string) {
   subprocess.on('exit', (code: string | null, signal: string) => {
     if (code) {
       fecLogger(LogType.error, 'Exited with code', code);
+      process.exit(code);
     } else if (signal) {
       fecLogger(LogType.error, 'Exited with signal', signal);
     } else {