[lld] [llvm] [DTLTO][LLD][ELF] Add support for Integrated Distributed ThinLTO (PR #142757)

[Fangrui Song via llvm-commits]

MaskRay wrote:

@bd1976bris The previous comment appears to report failures for the new test dtlto/files.test
```
# RUN: at line 34
z:\b\llvm-clang-x86_64-sie-win\build\bin\ld.lld.exe @l.rsp
# executed command: 'z:\b\llvm-clang-x86_64-sie-win\build\bin\ld.lld.exe' @l.rsp
# .---command stderr------------
# | ld.lld: error: cannot open Files\Python310\python.exe: no such file or directory
# `-----------------------------
# error: command failed with exit status: 1
```

https://github.com/llvm/llvm-project/pull/142757