Merge llvm-project release/19.x llvmorg-19.1.2-0-g7ba7d8e2f7b6

This updates llvm, clang, compiler-rt, libc++, libunwind, lld, lldb and
openmp to llvm-project release/19.x llvmorg-19.1.2-0-g7ba7d8e2f7b6,
a.k.a. 19.1.2 release.

PR: 280562
MFC after: 1 month

(cherry picked from commit 5deeebd8c6ca991269e72902a7a62cada57947f6)