Update macOS related documentation, broken links
@ocrete
Submitted by Olivier Crête Link to original bug (#773235)
Description
The macOS documentation needs to be updated, in particular, it refers to old versions of macOS and to PackageMaker which has disappeared from Xcode a while ago. So we should possibly have instructions on how to use it with pkgbuild/productbuild.
https://cgit.freedesktop.org/gstreamer/gst-docs/tree/sdk-installing-on-mac-osx.md
https://cgit.freedesktop.org/gstreamer/gst-docs/tree/sdk-mac-osx-deployment.md