partition-manager: 3.0.1 -> 3.3.1 (#40895)

The `3.0.1` build was broken (see the Hydra build from
https://hydra.nixos.org/build/74368257 for further reference).

Because of the missing `utillinux` build input the package fails fairly
early:

```
-- Checking for module 'blkid'
--   No package 'blkid' found
CMake Error at /nix/store/9hmhxgj4jk6jmxihgavj6gm0p759misc-cmake-3.10.2/share/cmake-3.10/Modules/FindPkgConfig.cmake:415 (message):
  A required package was not found
```

Additionally `partition-manager` was broken on non-KDE desktops (none+i3
in my case) as the plugins from `libsForQt5.kpmcore` couldn't be found
in `QT_PLUGIN_PATH` unless it's installed in
`environment.systemPackages` or with `nix-env -iA libsForQt5.kpmcore`.
This has been fixed by adding a wrapper in the `postInstall` hook which
prefixes the `QT_PLUGIN_PATH` with the plugin path from `kpmcore` used
for the build.