It was too ambitious to enable strictDeps all the time, as too many packages
need fixes. Now it is only enabled for Python packages and when cross-compiling.
nixpkgs now requires explicitly enabling or disabling Qt5 wrapping. This commit
disables wrapping by default, which breaks Qt apps that aren't overridden
manually in distro-overlay.nix, but fixes all the Qt libraries that don't need
wrapping. This is a sub-optimal solution, but matches the behavior that was
there before wrapping was made mandatory.
