[recipes] Add some notes on building a dmg

[Matthias Clasen <matthiasc src gnome org>]

commit ccf7e93f671258eba29c2ebb9fdc0f76ee734527
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Mar 5 09:39:08 2017 -0500

    Add some notes on building a dmg
    
    Since I won't remember in a few months...

 osx/README.md |   14 ++++++++++++++
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diff --git a/osx/README.md b/osx/README.md
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+The materials in this folder can be used to build a dmg of GNOME Recipes on OS X.
+
+The steps I've followed are:
+
+* Use the [GTK-OSX](https://wiki.gnome.org/Projects/GTK+/OSX/Building) jhbuild setup to build GTK+
+* Switch to the GNOME 3.24 moduleset and build a newer gtk+-3 and gnome-autoar
+* Build recipes, configuring it with --disable-gspell and --disable-canberra (I couldn't get those to build)
+* Install [gtk-mac-bundler](https://wiki.gnome.org/Projects/GTK+/OSX/Bundling)
+* Run ```gtk-mac-bundler ./org.gnome.Recipes.bundle``` in a jhbuild shell. This should produce a Recipes.app 
folder
+* Run ```./build-osx-installer.sh```. If all goes well, this produces a recipes.dmg image.
+
+Possible complications:
+
+* The template for the disk image might become too small again, as we are adding more recipes. It can be 
resized with the OS X disk utility.