Similarly to what is done on manylinux  speed up macOS build by re-using the build tree.

Similarly to what is done on manylinux (see [here](https://github.com/KitwareMedical/VTKPythonPackage/blob/5d217a5fb9b49146c3229488dd63410e2adc4f7c/scripts/internal/manylinux-build-wheels.sh#L17-L22)), the build process may be speed up by re-using the build tree.

_Originally posted by @jcfr in https://github.com/KitwareMedical/VTKPythonPackage/pull/30_