Since we track the SPV_ENV_... version with VkConfig.hpp, any other
directory that includes VkConfig has to have a dependency on SPIR-V
Tools.

Bug: b/172837769
Change-Id: I7962ee278c3240c9461acaedcd9cbbca0c08c0d6
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/50208Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Sean Risser <srisser@google.com>