gh-123748: Disable HACL SIMD256 on universal builds. by freakboy3742 · Pull Request #123927 · python/cpython
The native HACL implementation added in #119316 compiles fine on single architecture x86_64 and ARM64 macOS builds, but failed when compiled on universal2 builds. This is because the autoconf detection is based on the existence of the -mavx2 compiler flag; this flag is legal in universal builds (because the x86_64 compilation path supports the flag), but this then requires symbols that aren't available on ARM64 builds. A standalone ARM64 build disables this feature.
This PR modifies the autoconf check so that if -mavx2 support is detected and the build is universal2, the autoconf feature isn't enabled.