Merge llvm-project 12.0.1 release
This updates llvm, clang, compiler-rt, libc++, libunwind, lld, lldb and
openmp to llvmorg-12.0.1-0-gfed41342a82f, a.k.a. 12.0.1 release.
PR: 255570
MFC after: 6 weeks
(cherry picked from commit 4652422eb477731f284b1345afeefef7f269da50)