Rewrite ‘with pkgs.lib’ -> ‘with lib’

Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.

nixos/modules/virtualisation/qemu-vm.nix

@@ -7,9 +7,9 @@
 # the VM in the host.  On the other hand, the root filesystem is a
 # read/writable disk image persistent across VM reboots.
 
-{ config, pkgs, ... }:
+{ config, lib, pkgs, ... }:
 
-with pkgs.lib;
+with lib;
 
 let