Stop using old MAR format in the second esr60-based stable release
In legacy/trac#26362 (moved) we set MAR_OLD_FORMAT=1
when generating mar files for both release
and alpha
builds. In legacy/trac#26410 (moved) we remove it for the alpha builds after the first esr60-based alpha
is published.
This ticket is for removing it after the first esr60-based stable release is published.