`phase_3_run_analysis_passes` no longer exists, and AFAICT this code has
been refactored so much since this comment was written that it no longer
has any useful meaning.
If `-o -` or `--emit KIND=-` is provided, output will be written
to stdout instead. Binary output (`obj`, `llvm-bc`, `link` and
`metadata`) being written this way will result in an error unless
stdout is not a tty. Multiple output types going to stdout will
trigger an error too, as they will all be mixded together.
