Thanks for the report. This problem was reported previously in bpo-24844 and was determined to be due a partial implementation of atomics support in the early versions of LLVM compilers provided in the Apple Developer Tools for macOS 10.7. While the start of a patch was proposed there, it languished for lack of interest and the issue was subsequently closed by the submitter. Since you have already have a workaround (and using a newer compiler is a good idea in this), I think there will be little interest in reviving this issue.

By the way, since you need to continue to use macOS 10.7, you may want to consider using Python (and many other third-party packages) from the MacPorts project. They provide pre-built binaries for these packages, including the latest versions of Python 3.10, built for multiple versions of macOS including 10.7 Lion. I was able to install MacPorts and a fully functional Python 3.10.3 on a 10.7.5 system in fewer than 5 minutes.  https://www.macports.org/install.php#installing