cross-binutils doesn't build tools for 32-bit arches, since those can be served using the 64-bit tools. This is understandable, but unfortunately some external programs expect 32-bit utils to be present and don't really understand how to use the 64-bit tools.
I'd like to suggest adding wrappers that would pretend to be 32-bit tools, while actually just running the 64-bit tools with proper flags set. They could be shipped as e.g. a "binutils-i386-linux-gnu" package with a Requires: for "binutils-x86_64-linux-gnu".
Example wrappers for i386:
x86_64-linux-gnu-as --32 $@
x86_64-linux-gnu-ld -A elf32-i386 $@
x86_64-linux-gnu-gcc -m32 $@