Merge llvm-project main llvmorg-18-init-16864-g3b3ee1f53424
This updates llvm, clang, compiler-rt, libc++, libunwind, lld, lldb and
openmp to llvm-project main llvmorg-18-init-16864-g3b3ee1f53424.
PR: 276104
MFC after: 1 month
(cherry picked from commit 297eecfb02bb25902531dbb5c3b9a88caf8adf29)