Comment (by Roland Haas):

This triggered a bug in make version 3.81 that is described in #2345 and fixed in git hash 93d691f "Formaline: combine rules to make tarball and blob" of cactusutils.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2316/reduce-space-used-by-formalines-temporary