Add -T option to CLI to specify a temporary directory.

This does the same thing as setting $TMPDIR in the environment.

See change I43cf578da61978a3fb0baab6e93139210c5348e0 for the
corresponding commit in the `mw-ocg-latexer` package.

Change-Id: I1a9dc18bf1563ad13b40fba9ebc5093ee8c92bde