The s390x patch conflicts with both the ppc64le patch and the paxmark.
The PaX kernel is only supported for x86_64 so we can conditionally
apply the ppc64le, s390x or paxmark patch depending on arch.
Enable build on ppc64le backporting patches that enable rethinkdb
support on ppc64le and making necessary changes to build it.
This patch is a temporary solution until rethinkdb 2.4 release.