lf: fix panic error on systems where user is not in /etc/passwd

[GaetanLepage]

Description of changes

This fixes this issue which happens on systems where the user is not in /etc/passwd.
I submitted a fix upstream (to the lf repository) that solves this problem at the package level.
This PR adds the osusergo build tag to the derivation which ensures that the pure go implementation of os/user is used instead of the one relying on libc.
Indeed, the pure go implementations has a fallback for this case which consists in looking at the $USER and $HOME environment variables.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 22.11 Release Notes (or backporting 22.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.

@dotlambda

[SuperSandro2000]

darwin fails with:

2022/10/18 16:08:34 user: user: Current requires cgo or $USER set in environment
2022/10/18 16:08:34 $USER variable is empty or not set
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x40 pc=0x112ab63]

[GaetanLepage]

Oh ! Maybe the MacOS pure-go implementation of os/user cannot do anything more than looking at the $USER env variable...
Is it possible to set this option when not using darwin ?

[GaetanLepage]

@SuperSandro2000 I now apply the fix only when not using darwin. Tell me if this works for you :)

[SuperSandro2000]

I just looked at ofborg and that it failed there.

[SuperSandro2000]

otherwise LGTM