[MachO] Decl alignment

[bjorn3]

The alignment of data got ignored before.

Fixes #87

[m4b]

Wow this looked like a lot of work! Is there anyway we can add some kind of test for this ?

[bjorn3]

Wow this looked like a lot of work!

Several hours. (including finding amd reading machO docs and experimentally figuring out the correct way to pad the data)

Is there anyway we can add some kind of test for this ?

Maybe run objdump -rs to get section data and reloctions and then compare it against a fixed output. We could also add a main function to the prototype output and check alignment in there. Another would be running bingrep and checking all symbols are 8/16 byte aligned.

[m4b]

I'll squash and merge once the comment about why 0xaa is in

[bjorn3]

This is a breaking change as the alignment is now specified using an u64 instead of usize. I don't necessarily need a new release published, as the breaking change means that I need to update cranelift, which is blocked on bytecodealliance/cranelift#795.

[pchickey]

Published in 0.11.0