stdenv: partial revert of f2bb59e7

/cc @Ericson2314

PR was https://github.com/NixOS/nixpkgs/pull/46857

This line broke MacOS cross compilation. paxctl cannot be built on
macOS. Maybe it can be fixed, but no reason to break things
unnecessarily.

Regardless, you definitely need to be more careful about backporting.
I think it’s fine to move fast and break things on master but
with release-18.09 we should be more careful. Something like more
automated testing for cross compilation would also be
helpful (hopefully even making it block).

(cherry picked from commit f9c4075873cb56464126f993d22a1a72f7cfac45)