Not compiling on GCC 6.3

[Jonathan Farrugia]

In reference to earlier today's ticket at: HansKristian-Work/vkd3d-proton#212

I've tried to build dxil-spirv by itself without vkd3d but the compile still fails.

Steps I took:

1. extracted dxil-spirv itself.
2. extracted 'spirv-headers', 'spirv-cross' and 'spirv-tools' in their respective 'third_party' folder.
3. ran: 'meson . ./build' (folder I used for compilation)
4. 'cd build' and then 'ninja'

Let me know if there's anything else I could try.

[Hans-Kristian Arntzen]

Should be fixed now.

[Jonathan Farrugia]

@HansKristian-Work

Thanks that fixed it right away and I've successfully built the vkd3d library.