Fix crash while building opencv for OSX

[yonip]

The original crash was caused by scikit-build both prioritizes command line options over the parameters passed to the setup function, and that it defaults the command line options for -DCMAKE_OSX_DEPLOYMENT_TARGET and for -DCMAKE_OSX_ARCHITECTURES without checking that setup was passed those parameters.
(this is where scikit-build defaults the command line parameters, and this is where the command line parameters are combined with the passed in parameters).
As a workaround, I overrode one function in multibuild's common_utils.sh in config.sh that allows for extra command line parameters to be passed to setup.py, and set the parameters only for OSX tests in .travis.yml.
Also fix a later crash where install_run crashed on OSX builds with Python 3.7, where the TEST_DEPENDS environment variable defaulted to numpy==1.11.1 where Python 3.7 requires numpy==1.14.5.

[skvark]

Nice! Thanks a lot. I suspected that there was something overriding those params. Let's see how the builds go as I have been poking master branch today.

[jcfr]

Thanks @yonip for reporting the issue on scikit-build issue tracker and also thanks for your help to address the issue.

The problem should be fixed in the upcoming release of scikit-build, then specifying either plat-name macosx-10.7-x86_64 or -DCMAKE_OSX_DEPLOYMENT_TARGET:STRING=10.7 should have the expected effect.