Permit to test when building bindings separately from main library

[traversaro]

🦟 Bug fix

Follow up of #1491 . #1491 enable the compilation of bindings separately from the main library, but does not permit to set BUILD_TESTING:BOOL=ON in those binding-only builds.

Summary

This PR permits to pass -DBUILD_TESTING:BOOL=ON in bindings-only builds, by:

• Ensuring that ${PROJECT_BINARY_DIR}/include/test_config.hh is generated also in bindings-only builds,
• Use CMAKE_CURRENT_SOURCE_DIR instead of CMAKE_SOURCE_DIR when creating the tests, as the CMAKE_CURRENT_SOURCE_DIR variable have a consistent value that is not influenced on which is the root directory of the CMake build.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[traversaro]

@scpeters can we backport this to sdf14? Thanks!

[scpeters]

https://github.com/Mergifyio backport sdf14

[mergify]

backport sdf14

✅ Backports have been created

• #1577 Permit to test when building bindings separately from main library (backport #1509) has been created for branch sdf14 but encountered conflicts