Fix appimage creation

[teamyayc]

currently the appimage generated using linuxdeployqt on ubuntu 18.04 does not run properly on ubuntu 22.04, namely showing empty WebEngineView element and a stream of errors like

[37612:37615:0408/214422.123017:ERROR:validation_errors.cc(87)] Invalid message: VALIDATION_ERROR_MESSAGE_HEADER_UNKNOWN_METHOD 
[37555:37555:0408/214423.511735:ERROR:network_service_instance_impl.cc(262)] Network service crashed, restarting service.

Moreover, generating an appimage using the same tool on 22.04 through -unsupported options also produces an unusable appimage.
linuxdeploy with the qt plugin also seems to produce unworkable artifacts

[teamyayc]

currently still haunted by probonopd/linuxdeployqt#35.
Using the workaround described there allows the creation of an appimage running on 22.04, but not on 18.04 or 20.04.

Still better than nothing for the time being, this might be a first mitigation to this issue

[teamyayc]

Having appimage packages working reliably (and even just building reliably) with QtWebEngine seems to be a major issue.
For the time being this issue is put on hold. Instructions for building on linux are relatively clear and easy though.

[teamyayc]

on Hold