How to use with 18.09+?

[paulreimer]

I wish I knew how to cross-build RPi images using 18.09.

I gather some things have changed with cross-compilation in 18.09, and I think cross-compilation got simpler, but I can't figure it out.

I rebased your nixpkgs branch on release-18.09, and also tried without that override, but I seem to get a perl error:

nix-build -I nixpkgs=https://github.com/paulreimer/nixpkgs/archive/cross-nixos-aarch64-1.tar.gz system.nix -A config.system.build.sdImage -o sdImage
...
  /nix/store/jsrwk2mmhns5qvkh3y9wwdlqnrf7r7ya-nixos-sd-image-18.09.2327.37694c8cc0e-aarch64-linux.img-aarch64-unknown-linux-gnu.drv                                                                          
building
...
Checking perl version ... perl5-5.28.1                                                                                                                                                                       
No patchset found for perl5-5.28.1 in cnf/diffs                                                                                                                                                              
This perl version is probably not supported by perl-cross                                                                                                                                                    
ERROR: configure --mode=buildmini failed                                                                                                                                                                     
checking for stdint.h... yes                                                                                                                                                                                 
builder for '/nix/store/xm914bxrz8ykfbg3xl56swy0jbimndxj-perl-5.28.1-aarch64-unknown-linux-gnu.drv' failed with exit code 255                                                                                
cannot build derivation '/nix/store/anwd62j7wcyh8i08srbzahlw9dlp1hg7-nixos-system-nixos-18.09.2327.37694c8cc0e-aarch64-unknown-linux-gnu.drv': 1 dependencies couldn't be built                              
cannot build derivation '/nix/store/jsrwk2mmhns5qvkh3y9wwdlqnrf7r7ya-nixos-sd-image-18.09.2327.37694c8cc0e-aarch64-linux.img-aarch64-unknown-linux-gnu.drv': 1 dependencies couldn't be built                
error: build of '/nix/store/jsrwk2mmhns5qvkh3y9wwdlqnrf7r7ya-nixos-sd-image-18.09.2327.37694c8cc0e-aarch64-linux.img-aarch64-unknown-linux-gnu.drv' failed