[clang] [Clang] diagnosing missing Vulkan environment when using SPIR-V triple (PR #190840)

[Tony Guillot via cfe-commits]

to268 wrote:

The only thing remaining about general PR stuff is adding a line in the `ReleaseNotes.rst` (in the Clang sub directory in this case) in the appropriate section that is used to describe changes for each release.
I will reach out to the lead maintainer of Clang privately so he can assign the right people to review the technical part of the PR (since he has not done that already).

https://github.com/llvm/llvm-project/pull/190840