This now builds both the LLVM and Subzero Reactor backends.
Fixed issue where failures were not actually failing the build in continuous.bat.
Changed the test's expected path of vk_swiftshader.dll to more closely match macOS and Linux.

Bug: b/130458775
Bug: b/123360006
Change-Id: Id2cfc0a7016c9813597567fd6ab900fe4047b8f8
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/29109
Presubmit-Ready: Ben Clayton <bclayton@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>