Build error on ARM

[fgaz]

For some reason I only get this error on ARM while compiling the new evilpixie release

../src/file_save.cpp: In function 'void SaveLayer(const Layer&, const string&, const ProjSettings&)':
../src/file_save.cpp:107:39: error: no match for 'operator!=' (operand types are 'const Box' and 'Box')
  107 |             if (!grid.Empty() && grid != defaultGrid ) {
      |                                  ~~~~ ^~ ~~~~~~~~~~~
      |                                  |       |
      |                                  |       Box
      |                                  const Box

complete log: https://logs.nix.ci/?key=nixos/nixpkgs.205843&attempt_id=998a9684-4e26-4521-834b-37aeb3264487