Use more robust test for libatomics
Use more robust test for libatomics

Taken from Mesa configure script:

https://github.com/mesa3d/mesa/blob/17.2/configure.ac#L405-L427

rycee/nix,NixOS/nix,rycee/nix,ehmry/nix,ehmry/nix,rycee/nix,dtzWill/nix,dtzWill/nix,ehmry/nix,pikajude/nix,dtzWill/nix,rycee/nix,ehmry/nix,NixOS/nix,rycee/nix,NixOS/nix,NixOS/nix,pikajude/nix,ehmry/nix,pikajude/nix,dtzWill/nix,NixOS/nix,dtzWill/nix,ehmry/nix