Most of these come from LLVM 3.
I'd normally try hard to silence these warnings without modifying 3rd party code, but I indend to delete this dependency in the very near future.

Bug: b/130343040
Change-Id: Icf6003c58ad118989240d64cf480aa1e2e639fb7
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/29088
Presubmit-Ready: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Ben Clayton <bclayton@google.com>