To normally work on a multi processor machine.
If this flag is not set, the below error occurs with sphinx-build:
Warning, treated as error:
WARNING: the ext.remote extension does not declare if it is safe
for parallel reading, assuming it isn't -
please ask the extension author to check and make it explicit
Change-Id: I306c8b8db27a930e860c669b32d97c3a0fbbc32f