Test coverage for AArch64 problem spots
Squashed 'ffi-mini/' changes from e4731ef..4c9f534

4c9f534 libffiv3.0.14-rc0-WIP: zwaldowski/libffi-iOS@1020c1d

git-subtree-dir: ffi-mini
git-subtree-split: 4c9f5345fb9453763eb11e3999b4f41688f5ebe3