Add missing Categories for generating default.desktop file

[lenrys29]

Hi,

We've got this error while using linuxdeployqt without desktop file :

linuxdeployqt  (commit 6fcaf74), build 55 built on 2023-09-23 13:33:41 UTC
WARNING: Not checking glibc on the host system.
         The resulting AppDir or AppImage may not run on older systems.
         This mode is unsupported and discouraged.
         For more information, please see
         https://github.com/probonopd/linuxdeployqt/issues/340
Not using FHS-like mode
app-binary: "~/my_project/install/app/my_application/my_application"
appDirPath: "~/my_project/install/app/my_application"
relativeBinPath: "my_application"
ERROR: Desktop file missing, creating a default one (you will probably want to edit it)
ERROR: Icon file missing, creating a default one (you will probably want to edit it)
appimagetool, continuous build (commit 8bbf694), build <local dev build> built on 2020-12-31 11:48:33 UTC
NOTE: Using the output of 'git rev-parse --short HEAD' as the version:
      16c130f
      Please set the $VERSION environment variable if this is not intended
Desktop file: ~/my_project/install/app/my_application/default.desktop
Categories entry not found in desktop file
.desktop file is missing a Categories= key

[probonopd]

Well, if you do it like this, then less skilled developers may just go with "Utility" rather than putting together a proper desktop file. Hence, the provided template. Maybe Categories=PutInAValidCategoryHere would be better.

[probonopd]

Also, you are using unsupported command line arguments. This is highly discouraged! For more information, please see

• Latest continuous linuxdeployqt build does not work on Ubuntu 16.04 LTS and openSUSE Leap 15.0 #340