The use of named anonymous file mappings was only meant for the
allocation of executable memory by the Reactor JIT.

Bug: b/174801963
Change-Id: Ifae13c7ed5cdbb7d940cea750d3f061d08e9f442
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/50889
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>