Python environment on FreeBSD 14

[gilles-peskine-arm]

When we upgraded FreeBSD executors to FreeBSD 14 (current release at the time), we could no longer set up our Python environment.

We have a working Python environment on FreeBSD 12 but that is not a satisfactory solution: that version of FreeBSD is not only no longer maintained, but it's become practically impossible to install (you can get the base system but not the packages).

[bensze01]

The issue is caused by the dependence of cryptography >=35.0.0 on a Rust toolchain when it is built from source.
Since PyPI doesn't support binary distribution of wheels on the BSDs, we are forced to use source packages, causing min_requirements.py to fail.

I've raised a PR that works around this issue, as well as a Jira ticket requesting the installation of a Rust toolchain on the FreeBSD AMIs.