The idea here is that we can build a number of fine granularity SPIR-V tests, which we can also verify against any optional system Vulkan hardware.

This CL adds support for building and running the Vulkan unit tests on mac and linux.

Bug: b/123749916
Change-Id: I01a4e2a914ffd5473d271013957fa3dddbc43645
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/24328
Presubmit-Ready: Ben Clayton <bclayton@google.com>
Tested-by: Ben Clayton <bclayton@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>