pin dmgbuild version

When run with v1.2.0 the build fails with:

dmgbuild -s dmg_settings.py LBRY lbrynet.0.7.7.dmg
Traceback (most recent call last):
  File "[..]/2.7/bin/dmgbuild", line 36, in <module>
    dmgbuild.build_dmg(args.filename, args.volume_name, args.settings, defines=defines, lookForHiDPI=args.lookForHiDPI)
  File "[..]/2.7/lib/python2.7/site-packages/dmgbuild/core.py", line 440, in build_dmg
    d['.']['pBBk'] = background_bmk
  File "[..]/2.7/lib/python2.7/site-packages/ds_store/store.py", line 1183, in __setitem__
    entry_type = value[0]
  File "[..]/2.7/lib/python2.7/site-packages/mac_alias/bookmark.py", line 365, in __getitem__
    raise KeyError('Key not found')
KeyError: u'Key not found'

packaging/osx/lbry-osx-app/setup_app.sh

@@ -45,11 +45,8 @@ else
     pip install $MODULES
 fi
 
-pip install dmgbuild
-pip show dmgbuild
-
+pip install dmgbuild==1.1.0
 export PATH=${PATH}:/Library/Frameworks/Python.framework/Versions/2.7/bin
-dmgbuild --help
 
 pip install jsonrpc certifi