"-Wno-error=header-hygiene" was redundant with "-Wno-header-hygiene".
Removed it.

Change-Id: I5b75e8d42ef78c230cf064372f99db7950caf262
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/27868Tested-by: Alexis Hétu <sugoi@google.com>
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>