BUG: nixpkgs.hostPlatform is missing.

I updated my flake, after that I got this error:

error:                                                                                                                                                                                                   
       … while evaluating the attribute 'Yon.config.nixpkgs'                                                                                                                                             
         at /nix/store/irknf7niks2djxz4csh7sr44wwrs082y-source/lib/modules.nix:334:9:                                                                                                                    
          333|         options = checked options;                                                                                                                                                        
          334|         config = checked (removeAttrs config [ "_module" ]);                                                                                                                              
             |         ^                                                                                                                                                                                 
          335|         _module = checked (config._module);                                                                                                                                               
                                                                                                                                                                                                         
       … while calling the 'seq' builtin                                                                                                                                                                 
         at /nix/store/irknf7niks2djxz4csh7sr44wwrs082y-source/lib/modules.nix:334:18:                                                                                                                   
          333|         options = checked options;                                                                                                                                                        
          334|         config = checked (removeAttrs config [ "_module" ]);                                                                                                                              
             |                  ^                                                                                                                                                                        
          335|         _module = checked (config._module);                                                                                                                                               
                                                                                                                                                                                                         
       … while evaluating the option `_module.check':                                                                                                                                                    
                                                                                                                                                                                                         
       … while evaluating definitions from `/nix/store/irknf7niks2djxz4csh7sr44wwrs082y-source/nixos/modules/rename.nix':                                                                                
                                                                                                                                                                                                         
       … while evaluating the module argument `pkgs' in "/nix/store/irknf7niks2djxz4csh7sr44wwrs082y-source/nixos/modules/programs/pay-respects.nix":                                                    
                                                                                                                                                                                                         
       … while evaluating definitions from `/nix/store/irknf7niks2djxz4csh7sr44wwrs082y-source/flake.nix':                                                                                               
                                                                                                                                                                                                         
       … while evaluating the option `_module.check':                                                                                                                                                    
                                                                                                                                                                                                         
       … while evaluating definitions from `/nix/store/irknf7niks2djxz4csh7sr44wwrs082y-source/nixos/modules/rename.nix':                                                                                
                                                                                                                                                                                                         
       … while evaluating the module argument `pkgs' in "/nix/store/irknf7niks2djxz4csh7sr44wwrs082y-source/nixos/modules/programs/pay-respects.nix":                                                    
                                                                                                                                                                                                         
       … while evaluating the option `nixpkgs.localSystem':                                                                                                                                              
                                                                                                                                                                                                         
       … while evaluating the option `nixpkgs.system':                                                                                                                                                   
                                                                                                                                                                                                         
       (stack trace truncated; use '--show-trace' to show the full, detailed trace)                                                                                                                      
                                                                                                                                                                                                         
       error: Neither nixpkgs.hostPlatform nor the legacy option nixpkgs.system has been set.                                                                                                            
       You can set nixpkgs.hostPlatform in hardware-configuration.nix by re-running                                                                                                                      
       a recent version of nixos-generate-config.                                                                                                                                                        
       The option nixpkgs.system is still fully supported for NixOS 22.05 interoperability,                                                                                                              
       but will be deprecated in the future, so we recommend to set nixpkgs.hostPlatform.

After adding:

nixpkgs..hostPlatform = lib.mkDefault "x86_64-linux";

to my system, everything worked again.
Maybe this could be automatically set by this lib.

Start by reproducing the reported flake evaluation and inspect flake.nix together with the system configuration that produces the missing nixpkgs.hostPlatform error. Done means the library handles this configuration without requiring a manual hostPlatform setting, with the relevant evaluation succeeding.