gimp 3.0.0~RC1 fails to build on s390x because of a timeout during the build.

Earlier this year, 2.99.18 completed the build stage successfully on
s390x (but had some issues with running the build tests later). The
gimp developers say there were 1892 commits between 2.99.18 and 3.0.0
RC1. And I haven't verified whether 2.99.18 continues to be buildable
on s390x.

I have tried these in my Ubuntu 25.04 PPA:
- moving the documentation build to arch: all since the initial
timeout appeared to happen there. That didn't make a difference (but
I've pushed that change to Salsa anyway).
- setting dh_auto_build --no-parallel

I did not get good error information since something just hangs (times
out) instead of giving a specific error.

It hung at:
[2560/2581] cc  -o app-tools/gimp-debug-tool-3.0

so I tried disabling the app-tools build and then it hung on the previous step:
[2558/2579] c++  -o app/gimp-3.0 app/gimp-3.0.p/main.c.o

I am strongly leaning towards removing gimp on s390x soon to allow
other Debian users to use gimp 3 for Debian Trixie.

Thank you,
Jeremy Bícha

I'm retitling this bug since gimp 3.0.6 fails in a similar way on the
other big-endian architectures, ppc64 and sparc64. powerpc is also
big-endian but its build tests fail before this point.

m68k is also big-endian but doesn't hit this failure. I don't know
why. Skipping dh_auto_test on s390x is not enough to avoid this
failure.

I'm setting Build-Depends: architecture-is-little-endian now. The only
architecture-independent reverse build dependency is gimp-texturize
which wouldn't be useful without gimp. gimp 3 only built on m68k for
the first time today after I fixed a blocker in gegl. It seems less
wasteful to have builds knowingly hang for hours. It's easy to remove
that Build-Depends restriction and do a test build in an Ubuntu PPA if
someone wants to check if the failure is fixed in a newer gimp
version.

Thank you,
Jeremy Bícha

I added back the m68k build of gimp.

Thank you,
Jeremy Bícha