All the patches previously applied, except the one from bug 1279096,
are either irrelevant (as pertaining to changes to the upstream build
system we don't use anymore), were applied upstream, or the issue they
fixed were fixed differently upstream.
Two additional patches, sent upstream as
https://github.com/libffi/libffi/pull/579 and
https://github.com/libffi/libffi/pull/580, are needed to fix our build
with, respectively, mingw-clang and GCC.
Our build system is adjusted according to upstream's configure.ac
and configure.host.
Differential Revision: https://phabricator.services.mozilla.com/D87824
