Snippets for cbmc 6.11.0 from Nix aarch64-darwin

Sourced from https://hydra.nixos.org/log/rw1qh5j15kxy8sls98si0i27k5if8mx8-cbmc-6.11.0.drv.

• __libcheck.c:314:32: warning: unknown warning group '-Wnonnull-compare', ignored [-Wunknown-warning-option]
    314 | #pragma GCC diagnostic ignored "-Wnonnull-compare"
        |                                ^