This is an attempt to speed up build times and avoid the flaky timeouts we're seeing with the LLVM debug builds.

Bug: b/147355576
Change-Id: I8dc83dd40a570849d02fe95822de534f0faae595
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/39956Tested-by: Ben Clayton <bclayton@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>