[llvm] [SPIR-V] Preserve available_externally linkage via NonSemantic.AuxData (PR #200002)

[Dmitry Sidorov via llvm-commits]

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@@ -0,0 +1,50 @@
+; -spirv-preserve-auxdata: emit NonSemantic.AuxData for attrs/metadata.
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MrSidims wrote:

For the tests, would it make sense to just adapt `--spirv-preserve-auxdata` tests from SPIR-V translator (forward path)? 

https://github.com/llvm/llvm-project/pull/200002