macOS package: Increase image size for dmg package

Increase to 300M to allow to build universal releases.
This is the maximum size of the release image, the final
file will be only at the usual compressed size.

extras/package/macosx/dmg/dmg_settings.py

@@ -27,7 +27,7 @@ appname = os.path.basename(application)
 format = defines.get('format', 'UDBZ')
 
 # Volume size (must be large enough for your files)
-size = defines.get('size', '150M')
+size = defines.get('size', '300M')
 
 # Files to include
 files = [ application ]