Merge llvm-project release/18.x llvmorg-18.1.5-0-g617a15a9eac9
This updates llvm, clang, compiler-rt, libc++, libunwind, lld, lldb and
openmp to llvm-project release/18.x llvmorg-18.1.5-0-g617a15a9eac9.
PR: 276104
MFC after: 3 days
(cherry picked from commit 5678d1d98a348f315453555377ccb28821a2ffcd)