Update to latest multibuild

[hugovk]

Fixes #76.

[hugovk]

Previously Linux failed (missing rsync) and macOS passed.

Now Linux passes and macOS fails. Logs end like:

Tests/test_util.py::TestUtil::test_is_not_path PASSED                    [ 99%]
Tests/test_util.py::TestUtil::test_is_not_string_type PASSED             [ 99%]
Tests/test_util.py::TestUtil::test_is_path PASSED                        [ 99%]
Tests/test_util.py::TestUtil::test_is_string_type PASSED                 [100%]
=================== 972 passed, 133 skipped in 41.82 seconds ===================
Modules should be: 'freetype2 littlecms2 pil tkinter webp'; but are 'freetype2 littlecms2 pil tkinter'

https://travis-ci.org/hugovk/pillow-wheels/jobs/348206873#L2469

Expected wep missing.

From https://github.com/python-pillow/pillow-wheels/blob/master/config.sh#L63-L67

[radarhere]

I have found that updating to Xcode 9.2 fixes the new problem - #79.