bug#29464: gcc-7 breaks guile-2.2.2?

[Dan Kegel]

Building guile-2.2.2 seems fine on Ubuntu 17.04, but fails with

Warning: Unwind-only `out-of-memory' exception; skipping pre-unwind handler.
FAIL: test-out-of-memory
==================================
1 of 39 tests failed
Please report to address@hidden

on Ubuntu 17.10.  libgc is the same version on both, but gcc is different...
and if I pick gcc-6 on ubuntu 17.10 (instead of the default gcc-7),
it seems to succeed.

Mentioned at
https://bugs.launchpad.net/ubuntu/+source/guile-2.2/+bug/1734575
https://lists.gnu.org/archive/html/guile-user/2017-11/msg00062.html
Possibly related to
https://lists.gnu.org/archive/html/help-guix/2017-11/msg00016.html