bug#18261: Apparently intermittent failures to build gegl

[mhw]

It is interesting the in the following evaluation

  http://hydra.gnu.org/eval/98371

gegl newly succeeds on x86_64, and newly fails on i686.

Both the earlier failure on x86_64 and the new failure on i686 involve
the failing test "run-rgbe-save.xml.sh".  I wonder if this is an
intermittent failure or if it depends on which build machine is being
used.

"run-clones.xml.sh" also fails on the new i686 failure, but not in the
most recent x86_64 failure, but maybe that's intermittent as well.

      Mark