Avoid parallel build with Sphinx before 1.4
Avoid parallel build with Sphinx before 1.4

As Ubuntu 16.04 has v1.3 and it crashes when you use -j

webmaster128/botan,randombit/botan,webmaster128/botan,randombit/botan,randombit/botan,randombit/botan,webmaster128/botan,webmaster128/botan,randombit/botan,webmaster128/botan