Implement ekam-client -f

[xortive]

This mode prints only failures, and prints failures when they happen
(meaning even when ekam is not sure if they are a true failure or caused
by a missing dependency.) This is noisy as there are a lot of "false"
errors, but is an easy way to get much quicker feedback when iterating
on headers that are included in lots of places, where before this you'd
otherwise have to wait for the entire build to settle before seeing errors.

[kentonv]

Hmm, why would you want to hide the successful actions? If anything, that seems like it should be a separate flag?

[kentonv]

I'd say the two flags should be:

• -q: Quiet mode: Don't show successful actions. Only show errors.
• -b: Show blocked: Show error logs from "blocked" actions which may resolve later in the build.

If it's just one flag then it should be:

• -M: Matt mode. Presents output the way Matt likes.

:)

[xortive]

I'm happy to split them up, as much as I would love to have a -M be part of ekam :p

I want to hide the successful actions because I can refer to the main ekam output to see that if I want -- my use case for this command is when I'm iterating on headers, so usually all I care about is seeing compiler output as quickly as possible.