Drop obsolete libffi Makefile
This patch drops obsolete libffi Makefile from the tree, given it's completely unused since removal of make build system in !7094 (closed).
Due to a large amount of spam we do not allow new users to create repositories, they are "external" users. If you are a new user and want to create a repository, for example for forking GHC, open a new issue on ghc/ghc using the "get-verified" issue template
This patch drops obsolete libffi Makefile from the tree, given it's completely unused since removal of make build system in !7094 (closed).