The libffi submodule in .gitmodules tracks branch darind/v8-ios, which no longer exists on https://github.com/NativeScript/libffi (see branches).
This causes git submodule update --init --recursive --remote to fail with:
fatal: Unable to find refs/remotes/origin/darind/v8-ios revision in submodule path 'libffi'
The branch reference should be updated to whichever branch is current (master?).