Added proper definition of ucontext for macos/aarch64 to avoid unaligned issue

[ptitSeb]

Added proper definition of ucontext for macos/aarch64 to avoid unaligned issue

For #4072

[sug0]

Some of my team mates at @heliaxdev have suggested that a better fix might be to invoke read_unaligned, which does not check for the alignment of the ucontext pointer. If we implemented a fix based on read_unaligned, we would not need to redefine ucontext_t for different platforms/architectures. Once I have some disposable time to work on this issue again, I'll investigate this possibility. That said, otherwise, lgtm.

[ptitSeb]

Some of my team mates at @heliaxdev have suggested that a better fix might be to invoke read_unaligned, which does not check for the alignment of the ucontext pointer. If we implemented a fix based on read_unaligned, we would not need to redefine ucontext_t for different platforms/architectures. Once I have some disposable time to work on this issue again, I'll investigate this possibility. That said, otherwise, lgtm.

Well, I think I'll merge this fix for now then. If you get a better fix with read unaligned, feel free to do a PR with it.