Merge llvm-project release/18.x llvmorg-18-init-18361-g22683463740e

This updates llvm, clang, compiler-rt, libc++, libunwind, lld, lldb and
openmp to llvm-project release/18.x llvmorg-18-init-18361-g22683463740e.

PR: 276104
MFC after: 1 month

(cherry picked from commit 878ed4957e077721efaf90ab5b70dce86dc94f4b)