Currently, when git describe fails to get a git tag for the OBS Version,
a non-fatal message is printed, and the generator is left to continue,
usually ending up with a more cryptic error message down the line.
Instead, print the git output together with a short description of what
actually happened, and exit fatally so the problematic line of code is
clear. An added advantage is that the git output is printed in red
instead of (say) white on color-enabled terminals.
If the `git describe` command fails we want to fall back to a default
version. _OBS_DEFAULT_VERSION is not in the same format as the string
returned by `git describe` though. In the event that the command fails
just use _OBS_DEFAULT_VERSION directly rather than trying to parse it.
Fixes: cmake fails if git is not installed but .git/ exists #6940
Status output related to OBS configuration is prefixed with the string
"OBS" and added padding for enabled and disabled features. This padding
was not aligned between platforms.
By moving the padding and prefix decoration into its own function,
both elements are controlled in a single place. CMake scripts were
changed to use this new function `obs_status` instead of using CMake's
`message` function directly.
