_obspython.so currently links directly against python as @rpath/Python
and has 3 common python install paths set as rpaths so it would only
work if a user had python installed at one of those hardcoded paths.
Don't link _obspython against python at all but instead link it with
"-undefined dynamic_lookup" so when it is imported by python all it's
undefined python symbols get resolved at runtime against the user
supplied python instance loaded into the process earlier.
The rpaths aren't needed anymore this way.
a44ff34ef0