[Tails-dev] mksquashfs for reproducible squashfs

Hi,
I will much appreciate if you can help me with the following:

Where I can find the exact command that tails use to generate a
reproducible filesystem.squashfs using mksquashfs?.

I have been following https://labs.riseup.net/code/issues/12032 but
all my attempt to create a reproducible filesystem.squashfs have been
failed.
I have been using " -processors 1 -no-fragments "and i have compiled
my own mksquashfs based on Lamby patch to use SOURCE_DATE_EPOCH and i
cannot create a reproducible squashfs :(

Thanks for any help.
Best regards,
--
Andrés Pavez