flatpak: drop ld_library_path and use symlinks instead
Until https://github.com/flathub/io.qt.qtwebengine.BaseApp/pull/3 is accepted, this will make it better.
By some pure luck, 5.12 keyboard works without any additional recompile. So, I can use it for 5.14 as well. Looks like switching to 5.14 makes it better on HiDPI (not perfect though). However, LD_LIBRARY_PATH interferes with my hack for SFOS, hence my interest in cleaning it here. Also, we now include into Angelfish package qtwebengine. Probably no difference on device, but larger files during development. Otherwise, all is fine. (note that chromium version is the same though)