boxlayout: Do not infloop

boxlayout: Do not infloop

if the loop for determining max width grows too big, print an error and
abort assuming that a satisfactory value was reached.

This will cause wrong layout and might cause widgets to overlap, but it
will not infloop.

It actually works around and doesn't really fix the primary cause of the
following bugs, but good enough to close them:

(cherry picked from commit 515b1f52929a189b858a38aba733a3e7d2375fbc)

Bug: https://gitlab.gnome.org/GNOME/gtk/-/issues/4517
Bug-Debian: https://bugs.debian.org/1010547
Origin: upstream, 4.6.4, commit:ae0166973795e750f08b89f9f0ef974d7ac48bc7

Gbp-Pq: Name boxlayout-Do-not-infloop.patch