If for some reason librtc is not present, we could crash assert immediately instead of crash on a bad access.
<rdar://problem/129080708>
Pull request: https://github.com/WebKit/WebKit/pull/29395
Committed 279610@main (ae12b87cfbd4): <https://commits.webkit.org/279610@main> Reviewed commits have been landed. Closing PR #29395 and removing active labels.