zlib cannot be cross built from source for multilib-enabled
architectures unless adding the nobiarch build profile, because the
dependency on gcc-multilib is not satisfiable. As we do not have a
-for-host variant for this package, we can depend on
gcc-multilib-TRIPLET instead. This is a bit verbose, but we're not
likely to add more multilib architectures, so that feels like a sane
cost. I'm attaching a suitable patch.
This patch is supposed to establish a baseline of cross build support.
Once it is in, we may consider moving away from gcc-multilib. For
instance in a build for i386, we should be able to call
"x86_64-linux-gnu-gcc" instead of "i686-linux-gnu-gcc -m64" if we depend
on "gcc-x86-64-linux-gnu [i386] <!nobiarch>". It is equally verbose, but
removes one multilib user.
Helmut