It doesn't need autoconf to see this. I have seen it in a project with a simple ...

asveikau on Sept 5, 2019 | parent | context | favorite | on: Mach kernel

It doesn't need autoconf to see this. I have seen it in a project with a simple make -j, compiling with clang in both places. Builds finish much faster on Linux.

To be fair this may be many things and not just mach syscalls.