Fixes and improvements to the Linux readme

[mbmjertan]

Hey!

While building Librepods, I've noticed some errors in the Linux readme, as well places for improvement.

Changes:

• Added qt development header list for Fedora
• Added openssl development header dependency (this is bundled in the openssl package on Arch, but not in most other distros)
• PHONE_MAC_ADDRESS is no longer a build-time constant, but an environment variable
• The build target is librepods, not applinux

I've separated each change into a commit of it's own so you can easily cherry-pick the changes you want to apply if you don't want to set some.

Thank you for this project, hope this PR is welcome 😄

[kavishdevar]

Thank you so much for your contribution!