apply_updates.py applies the already downloaded files from the updates
folder and removes all the obsolete files from the bundle. It's meant
to be use by the pyinstaller bundle.

- Resolves: #7342
- Related: #5876

we won't be using this for packaging though.
it can be useful to avoid installing it, although installing from wheel is
quite straightforward in osx.

--use-leap-wheels sets --trusted-host (remove it when we have a proper
cert) and WHEELHOUSE to https://ftp.lizard.leap.se

Until we get ftp.lizard cname, use lizard as the wheels server.

- Related: #7339

generate_wheels uses $WHEELHOUSE to generate and store the wheels for
requirements.pip and requirements-testing.pip (if it exists).

pip_install_requirements.sh installs requirements.pip from them if
possible (if not, then it fetches them from pypi) or, if passed the
--testing flag, it installs requirements-testing.pip.

Related: #7327

to workaround the incompatibility problem with Qt libs found in ubuntu