[llvm] [DTLTO] [LLVM] Initial DTLTO cache implementation (PR #156433)

[Katya Romanova via llvm-commits]

romanova-ekaterina wrote:

> > Please also add llvm-lto2 based tests to llvm/test/ThinLTO/X86/dtlto, so that this gets exercised by LLVM tests.
> 
> This one was missed - the change needs some llvm-lto2 based tests as well.

I am working on the llvm-lto2 based test and I will post it in a separate commit.

https://github.com/llvm/llvm-project/pull/156433