Add ffi development lib to bindep

The ffi development library is necessary to build ipa.

Change-Id: I1c5c5a29e073774e93a6df6d754e1eb97aa9b86b

bindep.txt

@@ -5,6 +5,8 @@ python-devel [platform:rpm test]
 python3-devel [platform:rpm test]
 build-essential [platform:dpkg test]
 libssl-dev [platform:dpkg test]
+libffi-dev [platform:dpkg test]
+libffi-devel [platform:rpm test]
 
 # these are needed for functional tests
 mdadm [test]