[clang] [llvm] [MC] Remove UseAssemblerInfoForParsing (PR #91082)

[Peter Smith via cfe-commits]

https://github.com/smithp35 commented:

The code-changes look good, what I'm less sure about is whether this is the right thing to do unconditionally. 

A few months ago I would likely to have said this wouldn't matter that much as most people don't use `-S` in there build systems so any failures are likely to have been of minor incovenience. However we recently encountered a customer using `-save-temps` on their main build, which produces assembly and then re-assembles it; in our case there was a problem with describing the target to the assembler so that step failed.

With this in mind I'm a bit reluctant to say that this wouldn't affect anyone's use case.

This could be worth a RFC on Discourse to see if there is wider support or just apathy?

https://github.com/llvm/llvm-project/pull/91082