[llvm] [DirectX] Set whole-module flags prior to evaluating per-function flags (PR #139967)

[Farzon Lotfi via llvm-commits]

farzonl wrote:

> > I think the bugs you are fixing were mostly found because of the validator? Should we be doing some testing that invokes the validator something similaor to what `llvm/test/tools/dxil-dis/` tests do?
> 
> Yes, the bugs were found in the validator. Unlike dxil-dis, dxv (the validator) isn't included as a tool with LLVM. Perhaps dxv should be made available as llvm-dxv perhaps?
> 
> Or, the DirectX tests could have RUN lines conditioned on having dxv in the path, and runs the validator if it is in the path; similar to spirv-val I saw in SPIRV tests.
> 
> Either way, I think this topic should be relegated to a separate issue and PR.

`dxil-dis` is built by checking out and building DXC via the `LLVM_INCLUDE_DXIL_TESTS` Cmake argument. That means `dxv` probably exists somewhere in the llvm tools DXIL bin directory.

https://github.com/llvm/llvm-project/pull/139967