osx: don't launch installer after building it with bdist_mpkg bdist_mpkg do for some reason default to use the parameter --show ("Open with Installer.app after building") if no parameters are specified. We do not like that. All the important parameters to bdist_mpkg are already specified in setup.py and we don't have any to specify in the Makefile. Instead, specify the parameter '--' which do no harm but will disable the default opening of the installer. This makes it possible to build packages "silently".