feat(setup): support using system CMake

[mgorny]

Description

Add the dependency on PyPI cmake package only when the system tool is not available, and use it otherwise.

Motivation and Context

This avoids an unnecessary dependency on a third-party binary package, and improves portability by letting users benefit from downstream patching.

close #187

• I have raised an issue to propose this change (required for new features and bug fixes)

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds core functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)

Implemented Tasks

Checklist

Go over all the following points, and put an x in all the boxes that apply.
If you are unsure about any of these, don't hesitate to ask. We are here to help!

• I have read the CONTRIBUTION guide. (required)
• My change requires a change to the documentation.
• I have updated the tests accordingly. (required for a bug fix or a new feature)
• I have updated the documentation accordingly.
• I have reformatted the code using make format. (required)
• I have checked the code using make lint. (required)
• I have ensured make test pass. (required)

[mgorny]

For the record, make lint fails on existing code (i.e. unrelated to my changes).

[XuehaiPan]

It generally looks good. I have tested it locally, and it works as expected.

I have raised a discussion in the original issue.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (6808d38) to head (691dcea).
Report is 50 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #188   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           36        36           
  Lines         3786      3786           
=========================================
  Hits          3786      3786           

Flag	Coverage Δ
unittests	100.00% <ø> (ø)

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[XuehaiPan]

Hi @mgorny, I tweaked some of the changes in this PR. Let me know if you are fine with the changes. Then we can get this merged. Thanks!

[mgorny]

WFM, thanks!