bug#34157: Hydra: mozjs-60 builds on x86_64 and i686 seemingly get stuck

[Mark H Weaver <mhw@netris.org>]

Yesterday on Hydra, I found both Intel mozjs-60 builds seemingly stuck
while exporting the source checkout to hydra.gnunet.org.  One had been
going for ~22.5 hours, and the other for ~12 hours.  I forcefully killed
them and restarted them.  Now I see the same thing has happened on the
second attempt.  Both builds have been seemingly stuck like this for
about 19 hours:

  https://hydra.gnu.org/build/3342528
  https://hydra.gnu.org/build/3343511

In both cases, the build logs are empty, and the hydra log ends with:

  sending 1 store item to 'hydra.gnunet.org'...
  exporting path `/gnu/store/j2sz7dg35vkcz38sim71jll2ix1nk554-mozjs-60.2.3-2-checkout'

Of course, it's possible that they're not really stuck, but that they're
merely taking a ridiculously long time to send the source checkout to
the build slave.  My personal checkout of the mozilla-esr60 branch,
without the .hg directory, is about 2.1 gigabytes.

What do you think?

      Mark