Windows 64 mar files are not generated
Currently our Windows 64 build does not produce mar files.
As found by GeKo, it is due to using a 64bit mar tool in a 32bit container. We are building the firefox part in a 64bit container, creating a 64bit mar tools, but the final step is done in a 32bit container to use a 32bit nsis as a workaround for #23561 (moved).