Subzero is now lagging behind LLVM in terms of functionality.
Stub a new Capabilities, pre-populated with the Call() feature (implemented in a follow-up change).

With this we can skip tests that are known to not pass.

Bug: b/130746922
Change-Id: I033b63034a6dccd31418b1d1898114adbd718025
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/29409
Presubmit-Ready: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Ben Clayton <bclayton@google.com>