libcpp assertions got disabled on down-levels in 277723@main because older versions of Xcode do not support `CLANG_CXX_STANDARD_LIBRARY_HARDENING`.
Pull request: https://github.com/WebKit/WebKit/pull/28203
Committed 278441@main (dc2c6e2bbb6a): <https://commits.webkit.org/278441@main> Reviewed commits have been landed. Closing PR #28203 and removing active labels.
<rdar://problem/127643584>