busybox shell: enable various useful/expected features
busybox shell: enable various useful/expected features

Matches changes made in nixpkgs:
https://github.com/NixOS/nixpkgs/pull/34628

dtzWill/nix,zimbatm/nix,ehmry/nix,zimbatm/nix,NixOS/nix,NixOS/nix,vcunat/nix,vcunat/nix,layus/nix,ehmry/nix,peti/nix,dezgeg/nix,zimbatm/nix,dtzWill/nix,pikajude/nix,shlevy/nix,shlevy/nix,shlevy/nix,shlevy/nix,layus/nix,layus/nix,dtzWill/nix,shlevy/nix,ehmry/nix,rycee/nix,dezgeg/nix,ehmry/nix,NixOS/nix,ehmry/nix,dtzWill/nix,rycee/nix,layus/nix,NixOS/nix,dezgeg/nix,ehmry/nix,rycee/nix,peti/nix,vcunat/nix,peti/nix,peti/nix,peti/nix,vcunat/nix,dezgeg/nix,pikajude/nix,pikajude/nix,dtzWill/nix,zimbatm/nix,rycee/nix,dezgeg/nix,rycee/nix,layus/nix,NixOS/nix