chore: use .once instead of .on

Author: caoxiemeihao

scripts/watch.mjs

@@ -39,11 +39,10 @@ function watchMain(server) {
       if (electronProcess) {
         electronProcess.removeAllListeners()
         electronProcess.kill()
-        electronProcess = null
       }
 
       electronProcess = spawn(electron, ['.'], { env })
-      electronProcess.on('exit', process.exit)
+      electronProcess.once('exit', process.exit)
       // https://github.com/electron-vite/electron-vite-vue/pull/129
       electronProcess.stdout.on('data', (data) => {
         const str = data.toString().trim()