The spice-gtk/default.nix expression provides an option, withPolkit,
to decide whether or not the library should be compiled with support
for polkit. Currently setting that argument to false results in a
build failure:
Run-time dependency polkit-gobject-1 found: NO (tried pkgconfig)
meson.build:207:0: ERROR: Dependency "polkit-gobject-1" not found, tried pkgconfig
It appears that at some point spice-gtk began requiring the meson flag
-Dpolkit=disabled in this case. This commit adds that flag when
!withPolkit.
4a701a51aa