Remove qmake from the project
qmake without qt is minimally useful. Moreover providing qt in only public-stack would mean it's never tested in our CI which makes its support questionable. Providing qt in flatpak sdk was ruled out after discussion with KDE developers.
Considering all of above, the best solution may be removing qmake from the project.See !647 (comment 113757590) and below for more context.
Closes #453 (closed)
Supersedes and closes !647 (closed)