Vertex shader function could not be compiled into pipeline

When trying to run Mortal Kombat XL on MacOS running Wineskin/crossover/MoltenVK I get the following errors.

```
[mvk-error] VK_ERROR_INITIALIZATION_FAILED: Shader library compile failed (Error code 3):
Compilation failed:

program_source:473:9: error: no member named 'gl_CullDistance' in 'main0_out'
out.gl_CullDistance[0] = out.o5;
~~~ ^
.
[mvk-error] VK_ERROR_INVALID_SHADER_NV: Vertex shader function could not be compiled into pipeline. See previous logged error.
err: DxvkGraphicsPipeline: Failed to compile pipeline
err: vs : VS_48c64a754f51018d85d9719a2c5751764481a5d6
err: fs : FS_bae6d9d5b407ddd219b7dcaeb457942a161fc78e
[mvk-info] Converting SPIR-V:
```

and

```
[mvk-error] VK_ERROR_INITIALIZATION_FAILED: Shader library compile failed (Error code 3):
Compilation failed:

program_source:686:9: error: no member named 'gl_CullDistance' in 'main0_out'; did you mean 'gl_ClipDistance'?
out.gl_CullDistance[0] = out.o0.z;
^~~~~~~~~~~~~~~
gl_ClipDistance
program_source:114:11: note: 'gl_ClipDistance' declared here
float gl_ClipDistance [[clip_distance]] [2];
^
```

I read that gl_CullDistance is not supported in Metal. https://github.com/KhronosGroup/SPIRV-Cross/issues/1403. @billhollings [here](https://github.com/KhronosGroup/MoltenVK/issues/1484) has suggested it might make sense to modify SPIRV-Cross to at least support compilation and setting an output value, even if it can't be used as an MSL built-in, and will have no actual affect on the rendering behavior.

My original downstream issue which contains more logging output is [here](https://github.com/Gcenx/WineskinServer/issues/184)

Many thanks.

No repository file or test is named in the report. Start by reproducing the logged SPIR-V-to-MSL conversion and tracing how gl_CullDistance is handled in SPIRV-Cross. Done means the reported shader compiles without the missing-member error and the requested output behavior is covered by a regression check.

Written by the indexing model from the issue text.