CMake failure with zstd, release 15.0.7 & 15.0.6 on OpenBSD

[ToCodeABluejay]

          This issue is still active. I can myself confirm that neither 15.0.6 nor 15.0.7 will build on OpenBSD. I receive the same CMake error as originally posted. I don't know why, if this issue was seemingly patched, this keeps being reproduced upon further releases.

Originally posted by @ToCodeABluejay in #59056 (comment)