If the linux64 mar-tools does not exist, we should use the other mar-tools available
tools/update-responses/update_responses we currently extract the linux64 version of the mar tools, and fail if it is not available. However in the case of nightly builds, we build each architecture separately, and don't have the linux64 mar tools available when generating incremental mars for the other archs.
mar program is always built for linux64, I think we could use any of the mar-tools to available.
This will however require that the nightly build machine is running an OS with a glibc more recent than the one used in the builds (so doing legacy/trac#32736 (moved) before we update the Windows and macOS builds to buster).