if Clas12root is in `$LD_LIBRARY_PATH`, the `cppyy` bindings fail at run time

[c-dilks]

If any Clas12root's libraries are present in your linker path, cppyy will attempt to load them and fail at run time; I tried multiple ways to prevent this, but it seems that cppyy is rather "agressive" when it comes to loading libraries.

Short-term workaround: if you use the Python bindings here, remove Clas12root from your linker path (e.g., LD_LIBRARY_PATH on Linux).

Long term solution:

• replace our cppyy-based bindings with something better and controllable
• re-enable meson test for the Python examples