Fix AppImage SSL/TLS certificate issue

[app4soft]

This is a fix for #899 and #835 issues.

Reference:

• AppImage built with lnuxdeployqt can't get work SSL connection probonopd/linuxdeployqt#621 (comment)

  Key points:

  • generate your own AppRun instead of default soft link to add some environment variables to make better compatibility
  • linuxdeployqt can generate AppImage directly, so just use -appimage is enough. The most important is append -extra-plugins=tls to bundle qt TLS plugin to support https

[trevorsandy]

The only necessary modification to the LeoCAD appveyor.yml is to copy your AppRun script to the AppDir folder before calling linuxdeployqt. The cat content will be the AppRun script file. See probonopd/linuxdeployqt#621 (comment) for more details.

- cp tools/setup/AppRun AppDir

Cheers,

[leozide]

Thanks for tracking this down, I've checked in a fix that works a little better than this PR.