Shallow clone xeus-cpp in ci

[mcbarton]

fetch-depth: 0 clones the whole xeus-cpp repo. We only need a shallow clone when building (the default), so this PR this option.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.56%. Comparing base (5e4a82b) to head (81d67d0).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #466   +/-   ##
=======================================
  Coverage   80.56%   80.56%           
=======================================
  Files          21       21           
  Lines         854      854           
  Branches       80       80           
=======================================
  Hits          688      688           
  Misses        166      166           

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[mcbarton]

This PR requires this PR #465 for the self hosted job to pass.

[JohanMabille]

You meant Shallow clone of xeus-cpp, not CppInterop, right?

[mcbarton]

You meant Shallow clone of xeus-cpp, not CppInterop, right?

@JohanMabille Yes that should say shallow clone of xeus-cpp. I made a similar PR in CppInterOp and forgot the change the text. I have fixed the PR title and commit message now.