spv-out: support version 1.4

[kvark]

Looks like 1.4 expects all global variables to be a part of the interface:

Starting with version 1.4, the interface’s storage classes are all storage classes used in declaring all global variables referenced by the entry point’s call tree.

[kvark]

@teoxoy unfortunately the test validation is blocked on a thing. Our make validate-spv has "vulkan1.0" environment hard-coded currently, so it doesn't pass validation. We need to select the environment based on the SPV version that we generate. We could do this, for example, by changing the naming scheme ("xxx.spv14asm"), or by having sub-folders inside, e.g "tests/out/spv/1.4".

[teoxoy]

I think it would be feasible to read the version from the file and map it to a vulkan version but that sounds quite involved.
We can go with a sub-folder for now - up to you.

[kvark]

I think we should just merge this with some sort of a workaround, not blocking for a general solution (be it subfolders or not). Even without a test would be fine, since it's not a regression.

[kvark]

@teoxoy PR now comes with the general solution that extracts SPV version from the comment

[teoxoy]

PR now comes with the general solution that extracts SPV version from the comment

That's great, thanks for addressing it here!