[Feature]: Source clone and build from the binary

[Caellian]

I was fixing up the man docs because pandoc has issues dealing with markdown used in the website and saw that there's a compilation guide in the man documentation.

This doesn't make sense because if someone already has a built version of conky, then they likely don't need this info.

Then I figured "what if it made sense" - conky could provide an argument that:

• clones conky from the git repo
• automatically starts ccmake, with current build flags enabled
• builds a modified flavor of conky and installs it

This would be a very convenient way of allowing people to modify their existing builds. There are however a few problems with it:

• it would have to be able to deal with system not having prerequisites installed.
• how does it go about updating package manager information?
• current CMake doesn't support hermetic builds, so the process would have to be restarted several times if some (additional) libraries are missing.
  • if the package manager installed some dependencies, it wouldn't be able to tell they're no longer needed.