Split Presubmit Checks

[kammce]

Split up the main linux and macosx presubmit checks into a Presubmit, MacOSX, and Cleanliness checks.

Parallelizing and distrubuting the checks across additional jobs should reduce the overall time contributes must wait to know if their code is valid and can be submitted into the codebase.

• Add clang tool binaries directly to project (removing the need to clone them from arm-* exception repo), making it easier to run tidy and other checks in the Cleanliness checks.
• Fixed homebrew installation check in setup script. Should only run the installer if the brew command does NOT exist.

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (master@4ee8271). Click here to learn what that means. The diff coverage is n/a.

@@           Coverage Diff            @@
##             master   #1395   +/-   ##
========================================
  Coverage          ?   47.2%           
========================================
  Files             ?     182           
  Lines             ?   10079           
  Branches          ?    4312           
========================================
  Hits              ?    4754           
  Misses            ?    1591           
  Partials          ?    3734           

Flag	Coverage Δ
unittests	47.2% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 4ee8271...cb1576b. Read the comment docs.