Is there a way to inhibit message3 from Elisp?

[Oleh Krehel <ohwoeowho@gmail.com>]

Hi all,

I think this option would be quite useful in general, if it's not yet
implemented, which I'm pretty sure it's not.

My particular use-case is that I'm doing completion in the minibuffer
with ivy.el, calling `shell-command-to-string' in the `post-command-hook'.
And when I enable `while-no-input' in my function, my minibuffer
contents get rudely interrupted by `call_process_cleanup' saying:

> "Waiting for process to die...done"

I'm sure that this message is needed and appericated, but I'd like to
have an option to suppress it. I think a variable like `inhibit-message'
that I could let-bind would be a good solution to my problem.

I've seen this question brought up a few times on the stack exchange
sites, what people tend to do is to `flet'-override the `message'
function.  It doesn't apply in this case, but the solution to this
problem would solve the other ones too.

Oleh