Enable libc++ assertions.
<rdar://100416021>
Pull request: https://github.com/WebKit/WebKit/pull/4720
Committed 254888@main (dc5502f840ef): <https://commits.webkit.org/254888@main> Reviewed commits have been landed. Closing PR #4720 and removing active labels.
Re-opened since this is blocked by bug 246062
Pull request: https://github.com/WebKit/WebKit/pull/8850
Committed 259122@main (a421349785f7): <https://commits.webkit.org/259122@main> Reviewed commits have been landed. Closing PR #8850 and removing active labels.
This caused a crash in a timing-function test, see https://bugs.webkit.org/show_bug.cgi?id=251352. This is probably a good thing :)