[clang] [PPC][InlineASM] Mark the 'a' constraint as unsupported (PR #96109)

[Fangrui Song via cfe-commits]

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@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -emit-llvm -triple powerpc64le-linux-gnu -verify %s
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MaskRay wrote:

I think one RUN line (powerpc64) is sufficient. Duplicating this for ELF/XCOFF isn't necessary.

`inline-asm-constraints-error.c` might be a better test name. You can reuse the test for other errors.

https://github.com/llvm/llvm-project/pull/96109