Remove process 'exit' listener when uninstalling

[cspotcode]

In this code, if is uninstalled, should remove the event listener to avoid running that code twice.

let uninstalled = false;
    const uninstall = () => {
      if(uninstalled) return;
      uninstalled = true;
      if (blobStore.isDirty()) {
        blobStore.save();
      }
      nativeCompileCache.uninstall();
    }
    process.once('exit', uninstall);