buildId is not an ad (#6851)
buildId is not an ad (#6851)

* Added a check for ad_ in the buildId

* ad_ > ad

Co-Authored-By: lfades <faea5242a00c52da62a0f00df168c199b7ab748d@zeit.co>

* Update the `ad` comment

Co-Authored-By: lfades <faea5242a00c52da62a0f00df168c199b7ab748d@zeit.co>

flybayer/next.js,azukaru/next.js,flybayer/next.js,BlancheXu/test,flybayer/next.js,BlancheXu/test,flybayer/next.js,JeromeFitz/next.js,JeromeFitz/next.js,azukaru/next.js,azukaru/next.js,BlancheXu/test,zeit/next.js,JeromeFitz/next.js,zeit/next.js,JeromeFitz/next.js,zeit/next.js,azukaru/next.js