[llvm] [CMake] Simplify building of bolt-optimized clang for distribution builds (PR #117772)

[Tom Stellard via llvm-commits]

tstellar wrote:

I noticed this wasn't working for the install targets, so I had to add clang-bolt as a dependency to the install targets too.

I wonder if would be better to have the install targets depend on the `distribution` target instead.

https://github.com/llvm/llvm-project/pull/117772