nixos-container: Ensure umask 022

Fixes #2585.

(cherry picked from commit 253bbb8e2bdae01403443d50acf5e98061750c43)
Don't enable the NVIDIA driver by default because it's unfree

(cherry picked from commit 1bd8ced9c0eb4002ffa2afb3e4a60c5bccfc28ef)
nixos-generate-config: Don't include /var/setuid-wrappers

(cherry picked from commit dc78ae327c5e20c5e24214c956be219fc8d213c2)
nixos-generator-config: Don't emit a double / in bind mounts

(cherry picked from commit 4b7c606589be8440c982dc19bc9497b13e82abce)
Add nifskope

(cherry picked from commit 535de5e45acac5a64e762fd674de946e09493a6a)