[clang] [Cygwin] va_list must be treated like normal Windows (PR #143115)

[via cfe-commits]

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@@ -0,0 +1,37 @@
+// RUN: %clang_cc1 -triple x86_64-windows-gnu -emit-llvm < %s | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-pc-cygwin -emit-llvm < %s | FileCheck %s
+
+// copy ms_abi block only from ../ms_abi.c
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jeremyd2019 wrote:

I think the idea was 
```suggestion
```

https://github.com/llvm/llvm-project/pull/143115