Use software collections on Redhat/Centos for desktop sync client and Qt packaging

[moscicki]

As discussed with @michaelstingl, @jnweiger, @SamuAlfageme.

Please review the work from CERN Linux team. Its about Software Collections on Redhat and packaging the client according to practices used on Redhat systems.

Ref: #2558 (comment)

[michaelstingl]

Currently we use OBS and as far as I know OBS is not capable of building repos in SCL (RHEL) or PPA (Ubuntu) format.

[guruz]

FYI @crrodriguez @dragotin

[moscicki]

It was mentioned to me by your team that you consider to drop SUSE build system altogether. That would be a step forwards. Please keep me posted about this development.

[fmoc]

We're using craft now to handle dependencies for the AppImage builds. Long term goal is to replace classic packaging (which for CentOS always has used some software collections) with those (or maybe provide packages that contain the AppImages' contents).