Hello, #68560 disables this failing test. You can apply that patch series or just add this build-phase to the leptonica package definition:
(add-after 'unpack 'disable-failing-tests
(lambda _
(substitute* "prog/Makefile.am"
(("ioformats_reg") ""); Fails for unclear reason.
(("pngio_reg") "")))) ; Fails non-deterministically.
Cheers,
Herman Rimm
