Merge llvm-project release/18.x llvmorg-18.1.4-0-ge6c3289804a6
This updates llvm, clang, compiler-rt, libc++, libunwind, lld, lldb and
openmp to llvm-project release/18.x llvmorg-18.1.4-0-ge6c3289804a6.
PR: 276104
MFC after: 3 days
(cherry picked from commit dfa39133b333f57ca3133bf6c71cd75be4c3e801)