First build with qt6 and cmake.
QET compil, but a lot of things don't work.
Build tested on debian sid and ubuntu 25.04.
Dependency needed under debian and ubuntu :
qtcreator cmake qt6-tools-dev qt6-svg-dev libsqlite3-dev
libkf6coreaddons-dev extra-cmake-modules libkf6widgetsaddons-dev
Those desktop MIME types were needed only with KDE up to 3.x, as it
used to have its own desktop-based MIME type system. KDE 3 is EOL for
many years now, and there are already XDG MIME types.
These files are the bare XML definitions, and they are automatically
generated by update-mime-database (part of shared-mime-info) on update
(e.g. by distro hooks) or manually. Keeping them in the sources, and
installing them, is definitely not correct, as qelectrotech.xml is
their canonical definition.
Hence, drop them from the sources, together with references to them.
