charm build -r and -R contradict each other

[kwmonroe]

In #569, we switched the default charm build to output a report and introduced a new flag -R, --no-report to override that behavior. It's possible that a user could include both flags, at which point the outcome could be confusing -- the last flag set would take precedent.

If charm build defaults to reporting, I would ask that we deprecate the -r, --report option and send a message to stderr that the flag is no longer needed and reporting can be silenced with -R, --no-report.