remove bunk libffi file

builds/libraries/libffi

-#!/usr/bin/env bash
-# Build Path: /app/.heroku/python/
-
-OUT_PREFIX=$1
-
-# Use new path, containing autoconf.
-export PATH="/app/.heroku/python/bin/:$PATH"
-hash -r
-
-
-echo "Building libffi..."
-
-SOURCE_TARBALL='https://cl.ly/2s1t1u3v0N0I/download/libffi-3.1.tar'
-
-curl -L $SOURCE_TARBALL | tar x
-
-cd libffi-3.1
-./configure --prefix=$OUT_PREFIX --disable-static &&
-make
-make install
-
-# Cleanup
-cd ..