Prevent wasteful busy cpu spinning

[permosegaard]

First of all, I'd like to say a huge thankyou for your work on cargo-make, it's replaced all of my previous make workflows!

Now, this pull request may seem rediculous, however the unstable ctrl-c implementation in it's current form
will busy loop a whole cpu core while it's running, impacting performance, battery life, etc.

There's probably a better way to approach this, but as a simple fix I have added a minimal sleep to the loop.

Happy to sign away any rights to the provided code, etc.

[sagiegurari]

@permosegaard thanks! looks good and i have to admit, i didn't write the original code so i'm not sure and don't think there is an issue with it

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 92.89%. Comparing base (3bb9729) to head (911d56d).

Files	Patch %	Lines
src/lib/command.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1045      +/-   ##
==========================================
- Coverage   92.90%   92.89%   -0.01%     
==========================================
  Files         118      118              
  Lines       24220    24221       +1     
==========================================
  Hits        22501    22501              
- Misses       1719     1720       +1     

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[sagiegurari]

@permosegaard can you please rebase? i think i solved the build errors already in master

[permosegaard]

I should be up-to-date with your master now, shout if you need any more changes :)

[sagiegurari]

@permosegaard merged, thanks.