Should have done this in my previous changes. These options aren't meant
to be exposed to dependee targets. This also allows us to disable/remove
these options on a given target, without depender targets adding them
back.

Bug: b/145758253
Change-Id: Ieaba6824554d74e65d313409916bdf9ce4fd6182
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/43928
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Tested-by: Antonio Maiorano <amaiorano@google.com>