[clang] [HLSL] Add NativeInt16Type langopt to control whether short type is supported. Enabled by default for all but HLSL. (PR #165584)

[Finn Plummer via cfe-commits]

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+// RUN: not %clang_dxc -enable-16bit-types -T lib_6_7 foo.hlsl -### %s 2>&1 | FileCheck %s
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inbelic wrote:

```suggestion
// RUN: not %clang_dxc -enable-16bit-types -T lib_6_7 %s -### %s 2>&1 | FileCheck %s
```

https://github.com/llvm/llvm-project/pull/165584