[llvm] [DirectX][ObjectYAML] Attempt to fix flaky PRIVPart.yaml (PR #206278)

[Vladislav Dzhidzhoev via llvm-commits]

dzhidzhoev wrote:

> I think it is a bad idea to transfer raw binary data via stdin on Windows. On Windows, standard streams (stdin, stdout, stderr) open in the text mode by default, which corrupts raw binary data, halts reading if it encounters a 0x1A byte (the Ctrl+Z EOF marker), etc.

Hundreds of obj2yaml and ObjectYAML tests do that, including many existing DXContainer tests, so, I guess, it should not be the root cause of the flakiness. Was similar observed observed for them as well?

https://github.com/llvm/llvm-project/pull/206278