c7f7fa467ec571d3b3fd7ae1d32429b74b18ad9c Trivial: update clang thread-safety docs url (Ben Woosley)
Pull request description:
From the defunct http://clang.llvm.org/docs/LanguageExtensions.html#threadsafety to https://clang.llvm.org/docs/ThreadSafetyAnalysis.html
Tree-SHA512: 5113c3933fccee7b45cace5d8dffa38b46ed9ad1422795d57843a20b276ed0e513bbf8d3d2bd28f55a46baf14a349871d7a635485785b93cb21baf8b8720c15a
Backport of Core PR14129