TRUST CI: mips(el)-unknown-linux-gnu Multiple Tests Failing

[posborne]

https://travis-ci.org/berkowski/nix/jobs/205534694

[berkowski]

Started on a PR but ran into lots of incorrectly defined constants (same with #534). Instead of throwing #cfg blocks everywhere I started a rust-lang/libc#543 to fill in some of the constants missing from libc. If that lands it should ease things here.

[Susurrus]

This has been resolved for a while now I think as these are now Tier 1 platforms.