set exit code properly from main side

src/vs/workbench/electron-main/main.ts

@@ -67,17 +67,19 @@ process.on('uncaughtException', (err: any) => {
 function quit(error?: Error);
 function quit(message?: string);
 function quit(arg?: any) {
+	let exitCode = 0;
 	if (typeof arg === 'string') {
 		env.log(arg)
 	} else {
+		exitCode = 1; // signal error to the outside
 		if (arg.stack) {
 			console.error(arg.stack);
 		} else {
 			console.error('Startup error: ' + arg.toString());
 		}
 	}
 
-	process.exit();
+	process.exit(exitCode);
 }
 
 function main(ipcServer: Server, userEnv: env.IProcessEnvironment): void {