[llvm] Improve file patterns for some backends. (PR #147633)

[Peter Collingbourne via llvm-commits]

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@@ -784,18 +784,20 @@ backend:NVPTX:
 backend:MIPS:
   - '**/*mips*'
   - '**/*Mips*'
+  - '**/*mips*/**'
+  - '**/*Mips*/**'
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pcc wrote:

Not sure, I was just cargo culting AMDGPU. https://github.com/actions/labeler doesn't say that anything besides `**` works.

https://github.com/llvm/llvm-project/pull/147633