This patch add a line at the end of the build like follows:
ccache (direct) hit rate: 98.7%; (preprocessed) hit rate: 0.5%; miss rate: 0.8%
--HG--
extra : rebase_source : 9c814745516d7b8b0db2056a1fa0df540a5a239a
As a first step, this moves PYTHON_UNIT_TESTS to moz.build as a passthru
variable. In the future, we could hook it up to |mach test|.
The __init__.py files may not need to be in the list, but I don't want to
change the list here.
