ci: Workaround macOS hdiutil out of space errors

ci: Workaround macOS hdiutil out of space errors

Workaround "hdiutil: create failed - No space left on device" by
letting hdiutil auto-detect the required disk space.  Keep the old
method around via documentation in case this issue arises again.

https://stackoverflow.com/questions/18621467/error-creating-disk-image-using-hdutil
https://apple.stackexchange.com/questions/156994/yosemite-hdiutil-create-failed-error-5341
https://asmaloney.com/2013/07/howto/packaging-a-mac-os-x-application-using-a-dmg/
https://github.com/autopkg/jps3-recipes/issues/57

Make this issue easier to detect by changing the build script
macosx_makePackage.sh to fail early if any individual command fails.
This includes fixing up optional parameters to use default values.

Re-enable the "Check artifacts" step of the "Post-Build" process now
that macOS builds are hopefully more reliable.