This cl fixes GCC warnings caused by using clang specific directives.
Also ran git cl format on modified files.

Bug: chromium:1122889
Change-Id: Ibdaa84ab8162228ae40934fc9be14379ba89ca59
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/48148
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>