[llvm] [DXIL] Add support for root signature flag element in DXContainer (PR #123147)

[Justin Bogner via llvm-commits]

================

----------------
bogner wrote:

What is this test trying to cover? There's only one entry function here since `@main` does not have "hlsl.shader" metadata, but if you change it to `@main #0` then we'll obviously get the error like in the -Error version of this test

https://github.com/llvm/llvm-project/pull/123147