Use old MAR format when generating the MAR files for the first esr60-based alpha

Esr52-based Tor Browsers don't understand the LZMA compressed MAR files. We need to create the MAR files for the first esr60-based release using the old BZIP2 format. This can be done by setting MAR_OLD_FORMAT=1 before generating both the full and the incremental MAR files.

We should remove that patch once we generate the MAR files after the first esr60-based release.