[lld] [llvm] DTLTO Cache optimization - rebased (PR #203971)

[Katya Romanova via llvm-commits]

romanova-ekaterina wrote:

A brand-new test has been added 4 days ago, and it fails on my PR but only on Linux and AArch64 (but not on Windows). 

I will set up Linux environment today and have a look why this test is failing. 

I will also make changes that Teresa suggested. Thank you for reviewing!

https://github.com/llvm/llvm-project/pull/203971