Added migrator for aarch64 and ppc64le

[mariusvniekerk]

This is a basic migrator for doing the Arch rebuild.

• We are purposefully ignoring noarch here and initially operating within a bounded set of packages.
• In order to determine if a package is migrated we take a look inside the conda-forge-config.yml and check for certain values. If those are present a package is skipped.
• The current set of constraints yields about 120 packages to run this migrator on.

Additionally, this also adds a refactor to allow using distributed instead of multiprocessing for performing the initial graph building.

[isuruf]

If azure doesn't support [skip ci] [ci skip], then we can add it here so that other CI doesn't run.

[mariusvniekerk]

Do the other platforms support something like [skip appveyor] [skip travisci] [skip circle] ?

Feels a tad dangerous relying on a relatively common feature not existing :P

[isuruf]

Appveyor does. Travis-CI can be implemented using conditions. For circle, we can modify fast-finish script

[isuruf]

Can we at least do [skip appveyor] before we do this?

[CJ-Wright]

Would you mind putting in a PR?

[isuruf]

I opened a issue at #452

[codecov-io]

Codecov Report

Merging #444 into master will decrease coverage by 1.03%.
The diff coverage is 4%.

@@            Coverage Diff             @@
##           master     #444      +/-   ##
==========================================
- Coverage   29.21%   28.17%   -1.04%     
==========================================
  Files           8        8              
  Lines         623      653      +30     
==========================================
+ Hits          182      184       +2     
- Misses        441      469      +28

Impacted Files	Coverage Δ
conda_forge_tick/update_upstream_versions.py	25.65% <0%> (-0.33%)	⬇️
conda_forge_tick/make_graph.py	0% <0%> (ø)	⬆️
conda_forge_tick/utils.py	69.74% <21.42%> (-6.45%)	⬇️

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[scopatz]

Seems to be failing CI

[mariusvniekerk]

ah its failing because of the moved out r stuff

[CJ-Wright]

Lgtm thank you very much!