[Clang][CMake] Set up distribution target for Clang-BOLT

Provide a way to install usable BOLT-optimized Clang
(clang + resource headers) using
`ninja clang-bolt install-distribution` with BOLT.cmake cache file
or `ninja stage2-clang-bolt stage2-install-distribution`
with BOLT-PGO.cmake cache file.

Reviewed By: phosek

Differential Revision: https://reviews.llvm.org/D140565