[commit: ghc] master: rel-notes: Mention libffi packaging change (e30d9ca)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/e30d9ca6641289daa02962c775e13346dcb4782a/ghc

>---------------------------------------------------------------

commit e30d9ca6641289daa02962c775e13346dcb4782a
Author: Ben Gamari <ben at smart-cactus.org>
Date:   Sat Sep 30 12:18:02 2017 -0400

    rel-notes: Mention libffi packaging change
    
    [skip ci]


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e30d9ca6641289daa02962c775e13346dcb4782a
 docs/users_guide/8.4.1-notes.rst | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/docs/users_guide/8.4.1-notes.rst b/docs/users_guide/8.4.1-notes.rst
index f525a81..107519d 100644
--- a/docs/users_guide/8.4.1-notes.rst
+++ b/docs/users_guide/8.4.1-notes.rst
@@ -239,3 +239,9 @@ Build system
   There is currently no explicit dependency between the two in the build system and such there is no way
   to notify ``base`` that the ``rts`` has been split, or vice versa.
   (see :ghc-ticket:`5987`).
+
+- GHC now ships with a snapshot of the ``libffi`` library, which is used for
+  foreign function invocation on some platforms. This was necessary as there
+  were numerous fixes which have not yet been incorporated into a ``libffi``
+  release. However, you can still use the ``--with-system-libffi`` ``configure``
+  flag to tell the build system to use the ``libffi`` installed on your system.