macOS error is:

cpython-3.15> ld64.lld: error: duplicate symbol: _Py_jit_entry
cpython-3.15> >>> defined in Python/ceval.o
cpython-3.15> >>> defined in Modules/_testinternalcapi/interpreter.o

I think this is a result of the change from python/cpython#142911. Splitting out the _testinternalcapi module into a extension may address this.

This only happens with optimized builds (pgo, pgo+lto) when --enable-exterimental-jit is enabled.

_Py_jit_entry was added to Modules/_testinternalcapi/interpreter.c‎ in python/cpython#143944. This should be extern when the module is statically linked (and when dynamically linked I think).