There's a merged pull request on the void-packages repository

json-c++: run all tests that don't require a git checkout
https://github.com/void-linux/void-packages/pull/37291

Description:
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Running the unit tests (including without a git checkout) [is documented here](https://github.com/nlohmann/json#execute-unit-tests).

#### Testing the changes
- I tested the changes in this PR: **briefly**

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