Merge llvm-project main llvmorg-19-init-18630-gf2ccf80136a0

This updates llvm, clang, compiler-rt, libc++, libunwind, lld, lldb and
openmp to llvm-project main llvmorg-19-init-18630-gf2ccf80136a0, the
last commit before the upstream release/19.x branch was created.

PR: 280562
MFC after: 1 month

(cherry picked from commit 0fca6ea1d4eea4c934cfff25ac9ee8ad6fe95583)