[llvm] [win][arm64ec] Fix duplicate errors with the dontcall attribute (PR #152810)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,21 @@
+; RUN: not llc -mtriple arm64ec-windows-msvc -o - %s 2>&1 | FileCheck %s
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arsenm wrote:

```suggestion
; RUN: not llc -mtriple=arm64ec-windows-msvc -filetype=null %s 2>&1 | FileCheck %s
```

https://github.com/llvm/llvm-project/pull/152810