I cannot reproduce this on an 11.5 Intel MacBook Pro using an 11.5 SDK targeting x86_64 10.9.

However, I can reproduce on a similarly configured M1 using the same OS and SDK but cross-compiling to single arch x86_64.

The issue here may reside in how configure handles cross-compiling for Apple. The current logic in configure is a bit opinionated about how things should work and this patch may have tickled things into not working.

My opinion is that configure should support various cross-compiling scenarios like this (including building non-fat x86_64 only binaries from an arm64 machine). However, it is clear from the implementation and comments in this issue and elsewhere that the CPython core devs want to limit which exact cross-compiling configurations are supported on Apple.

If the core developers say various cross-compiling scenarios aren't supported build configuration any more, I'll accept that and work around the limitation on my end. However, do note there is a significant possibility that Apple stops selling Intel machines for various product models in a few weeks. I suspect various people will want to continue their practice of building x86_64 only binaries for the indefinite future. Regardless of when the ARM only transition occurs, arbitrary restrictions like not supporting Apple arm64 -> x86_64 cross-compiling will disappoint a growing cohort of users over time. I would encourage investing in less opinionated configure logic to support Apple cross-compiling. I could potentially contribute patches in this area, since I've already taught python-build-standalone to cross-compile more robustly (including to targets like iOS).