Checks for Bug: line, licenses, clang-format (v 8.0.0) and gofmt.

These checks are performed by a separate kokoro instance.

Fixed up broken licenses that it found.

Counterpart: cl/286343852
Bug: b/144825072
Bug: b/141892461
Change-Id: If4ffda0b6144efe3cd5560cf17a6f4ad33bf985a
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/39708Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Tested-by: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>