[llvm] [BOLT] Enable cross compilation of runtime libraries (PR #101180)

[Gergely Bálint via llvm-commits]

bgergely0 wrote:

> Build directory layout mirrors source directory layout. But what about the install directory layout? (set `-DCMAKE_INSTALL_PREFIX` and do `ninja install`). I'm talking about installation, and I think Target is probably not wanted there.

Yes, you are correct, I missed the install step. 

https://github.com/llvm/llvm-project/pull/101180