Add Vulkan on Linux to release builds

[iwr-redmond]

Llama.cpp includes Vulkan Linux builds in addition to Vulkan Windows. It would be helpful to do the same for stable-diffusion.cpp as well, because Vulkan versions will work on almost any GPU.

Notably, the downstream sd.cpp.gui.wx project already builds for Vulkan on Linux as its default, with the CI script matching the Llama.cpp equivalent. Similarly, while the Nexa SDK does not yet include Vulkan on Linux builds, testing suggests that building a Vulkan wheel for Linux is already possible. These existing use examples both suggest that adding the Vulkan on Linux architecture here would not be unduly complex.