Consider adding notifications of progress

[emberian]

For example, when compiling a larger crate (say, librustc): you get:

$ rustc foo.rs

and you wait... you're not entirely sure if your compilation is going to succeed or fail. You sweat with the tension, wanting to alt-tab over to reddit but not certain if you have an impending error to fix.

We could print out a helpful message before trans that this crate is going to compile, possibly in the same situations we emit color. It's a bit non-traditional for a compiler to print anything in the case of success, though.

[emberian]

And it'd probably be good if it were only printed if rustc spent more than, say, 15 seconds in the previous passes. Otherwise it'd just be noise: it'll be done soon anyway.

[steveklabnik]

Triage: no change.

[pnkfelix]

this is a dupe of #22227 #24335, right?

(normally we resolve dupes by letting the one with lower issue number take precedence, but in this case I suspect it would be best to close this Issue in favor of #24335, which has a lot of concrete ideas in its proposal.)

[steveklabnik]

Agreed, for sure.