File _link of Package mingw64-libffi

<link project="windows:mingw:win64" package="mingw64-libffi" baserev="300d587b59b016909aea73217647c99b">
  <patches>
    <delete name="libffi-3.5.1.tar.gz"/>
    <apply name="project.diff"/>
  </patches>
</link>