Issue with `-fvk-use-entrypoint-name` : Mixed stage shader module not supported about slang

[csyonghe]

This is a limitation of the validation layer and the right fix to the problem is to make validation layer accept this kind of code.

[csyonghe]

Closing as it is not a Slang issue.

[natduca]

@csyonghe reopening so we can discuss where the bug should be fixed --- is the issue here that the spir created is correct, and we (someone in our world) should go fix the vulkan validation layers to do this right? I noticed this issue in vvl:
KhronosGroup/Vulkan-ValidationLayers#4350

And I notice that a pr for it just recently merged. Maybe the latest vvl will work? @mklefrancois can you check with newer vvl?

[natduca]

Talking to @mklefrancois we think this is probably fixed by KhronosGroup/Vulkan-ValidationLayers#4350 as noted above. Marking closed until we hear otherwise. If others hit this issue in slang, sugggest pulling latest vvl as "fix" for this issue.