Investigate -fno-semantic-interposition build option

Fedora 32 has a proposal to build python with with `-fno-semantic-interposition` for better performance (https://fedoraproject.org/wiki/Changes/PythonNoSemanticInterpositionSpeedup),
> We add the -fno-semantic-interposition compiler/linker flag when building Python interpreters, as it provides significant performance improvement, up to 27% depending on the workload. Users will no longer be able to use LD_PRELOAD to override a symbol from libpython, which we consider a good trade off for the speedup.

It would be interesting to investigate whether the same could be done for conda-forge Linux (and possibly MacOS) builds.