[PyROOT] Add workaround for frozen rootbrowse on MacOS
[PyROOT] Add workaround for frozen rootbrowse on MacOS

Since MacOS blocks our second thread to update the GUI, rootbrowse will
run the event loop in the main thread if the underlying system is MacOS.

This is a hotfix for ROOT-10787, but a general fix to enable the GUI in
Python script mode is still missing.

root-mirror/root,root-mirror/root,root-mirror/root,karies/root,olifre/root,olifre/root,karies/root,karies/root,root-mirror/root,karies/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,karies/root,olifre/root,root-mirror/root,olifre/root,olifre/root,olifre/root,karies/root,karies/root,karies/root,root-mirror/root,karies/root,karies/root,olifre/root,karies/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root