[Vuejs]-Global is not defined in Nuxt 2.5 and higher

After many hours of investigation I’ve figured out that problem was in this config:

extend(config, {isDev, isClient, isServer}) {
  if (isClient) {
    config.target = process.env.BUILD_TARGET || 'electron-renderer';
  }
})

Have ho idea why it all worked prior 2.5 and broke after, but here is the case