This doesn't fix the CMake build, but it allows me to run cmake so I can try a build more similar to Windows and Linux.
Pull request: https://github.com/WebKit/WebKit/pull/3910
Committed 254049@main (8a1864d290b2): <https://commits.webkit.org/254049@main> Reviewed commits have been landed. Closing PR #3910 and removing active labels.
<rdar://problem/99447230>