Proprietary AMD drivers (fglrx) causing fatal error in i387.h

This article was originally published at https://gist.github.com/joepie91/ce9267788fdcb37f5941be5a04fcdd0f. It should no longer be applicable, but is preserved here in case a similar issue reoccurs in the future.

If you get this error:

/tmp/nix-build-ati-drivers-15.7-4.4.18.drv-0/common/lib/modules/fglrx/build_mod/2.6.x/firegl_public.c:194:22: fatal error: asm/i387.h: No such file or directory

... it's because the drivers are not compatible with your current kernel version. I've worked around it by adding this to my configuration.nix, to switch to a 4.1 kernel:

{
  # ...
  boot.kernelPackages = plgs.linuxPackages_4_1;
  # ...
}