[llvm] Add pre-merge workflow for HLSL testing (PR #122184)

[Tom Stellard via llvm-commits]

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@@ -0,0 +1,26 @@
+name: HLSL Tests - macOS
+
+permissions:
+  contents: read
+  checks: write
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tstellar wrote:

Why do you need `checks: write` here ?

https://github.com/llvm/llvm-project/pull/122184