--- libffi notes ---
The libffi subdirectory is managed as a subtree.  Use subtree merging
to update from upstream, e.g.

$ git pull --squash -s subtree -Xsubtree=native/libffi libffi master (or other branch, if necessary)

The libffi subdirectory was originally mapped into the local repo as follows:

$ git remote add -f libffi [email protected]:atgreen/libffi.git
$ git merge -s ours --no-commit libffi/master
$ git read-tree --prefix=native/libffi -u libffi/master
$ git commit -m "Merge libffi as subtree"