Merge llvm-project main llvmorg-15-init-17826-g1f8ae9d7e7e4
This updates llvm, clang, compiler-rt, libc++, libunwind, lld, lldb and
openmp to llvmorg-15-init-17826-g1f8ae9d7e7e4, the last commit before
the upstream release/16.x branch was created.
PR: 265425
MFC after: 2 weeks