[clang] [Driver] Restore compiler-rt arch suffix for PS and Windows (PR #89775)

[Fangrui Song via cfe-commits]

MaskRay wrote:

> > My recollection of the past discussions is that we want users to switch to the new hierarchy.
> 
> Is Microsoft a "user" who agreed to this change? Was clang-vendors tagged on this discussion about a new file hierarchy? I don't recall it. The library name change is news to me, although if it took place in a Discourse category that I don't follow, possibly our sanitizer folks are aware and I am not.

I don't know. There hasn't been enough engagement from Microsoft contributors to Clang Driver and sanitizers.
We as a community have been relying on a few Windows parties (including Chromium, @mstorsjo, @tru) that actively discuss on LLVM.
My recollection is that the new compiler-rt file hierarchy has been repeated discussed on Discourses/llvm-project PR/issues in the past few years.
If a party does not actively participate in the discussions, others would have to try guessing their intention.

Indeed, we could use clang-vendors more frequently.

> 
> I probably should not have pulled the PlayStation bit into it. The situation I ran into is a distributed build using a fresh-built clang-cl and the Visual Studio libraries in order to build a Windows app with `-fsanitize`. (PlayStation might have a similar issue, I haven't fully investigated that yet. I think it is likely though.)
> 
> > I am not aware of the embedded directive? Do you embed a path to a compiler-rt library to the generated object files?
> 
> Not a full path, but a filename. I see @mstorsjo has a comment also along these lines. The filename is searched for on the usual library paths, which aren't necessarily known or available to the compiler.

OK, the problem is the magic `--dependent-lib=` filename that depends on the old/new file hierarchy.
I think the distributed build system users need to prepare a file hierarchy to get the intended `--dependent-lib=` , or turn off it with the recent `-frtlib-defaultlib`.
Otherwise, the filesystem probing of Clang Driver may not give the desired result, but it is up to the users to fix it.


https://github.com/llvm/llvm-project/pull/89775