Merge llvm, clang, compiler-rt, libc++, libunwind, lld, lldb and openmp
8.0.1 final release r366581. The only functional change is a fix for a
mismerge of upstream r360816, which properly restores the r2 register
when unwinding on PowerPC64 (See https://reviews.freebsd.org/D20337).

Relnotes: yes
PR: 236062
MFC after: 3 days
X-MFC-With: r349004