Enabling > SSE 2 support for default python installation while keeping compatibility with M1

[agoscinski]

From the conversation in PR #403

Should we add march at least to the default pip installation? https://github.com/lab-cosmo/librascal/blob/9a9fbdc29003dadceb1c5cf6fed39b59fa0ece45/setup.py#L31 Since march seems to potentially give speed ups for numerical code by enabling SSE 2 > instructions. https://stackoverflow.com/a/52660117

Originally posted by @agoscinski in https://github.com/lab-cosmo/librascal/issues/403#issuecomment-1089141451

No, because this would also fail when compiling the python binding on M1 CPU. If someone wants to put in the time to figure out a robust way to add back -march=native without breaking some platforms, we can do it later, but I would rather have something which works for now.

Originally posted by @Luthaf in https://github.com/lab-cosmo/librascal/issues/403#issuecomment-1089156434