All places this was raised look like safe usage to me.

Also shuffled some CMake code around so that compiler
warning settings all sit next to each other.

Fixes: b/148842417
Change-Id: I262d0fdacc7a88092cad0890504b0e475f750d47
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/40835
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Tested-by: Ben Clayton <bclayton@google.com>