Can't build raspberry pi

[rhoriguchi]

Describe the bug

Can't rebuild system with latest nixos-unstable commit fc4148a.

Seems to be related to:

• Rebuilding NixOS on Raspberry Pi 4 fails after commit 4014fb6 #155925
• nixos: use uniq in the type of system.build #155963

Steps To Reproduce

Steps to reproduce the behavior:

1. Set options: NixOS on ARM/Raspberry Pi 4
   • boot.loader.generic-extlinux-compatible.enable = true
   • boot.loader.raspberryPi.enable = true
2. Rebuild

Expected behavior

Should build.

Additional context

The unique option `system.build.installBootLoader' is defined multiple times. Definition values:
       - In `/nix/store/nax3fp0jxka9apfnglg2hw45i4n9ab70-nixos/nixos/nixos/modules/system/boot/loader/raspberrypi/raspberrypi.nix': "/nix/store/1n4s07415748vn60n3i631sk5njm0061-raspberrypi-builder.sh -c"
       - In `/nix/store/nax3fp0jxka9apfnglg2hw45i4n9ab70-nixos/nixos/nixos/modules/system/boot/loader/generic-extlinux-compatible': "/nix/store/azx04scfvy3y2x30hlipvkgsjvb04zvg-extlinux-conf-builder.sh -g 20 -t 5 

Notify maintainers

• @tkerber
• @ncfavier

Metadata

Please run nix-shell -p nix-info --run "nix-info -m" and paste the result.

 - system: `"aarch64-linux"`
 - host os: `Linux 5.10.52, NixOS, 22.05 (Quokka)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.6.0pre20211217_6e6e998`
 - channels(root): `"nixos"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

[wegank]

Duplicate of #155925