[v9_16] Add 32-bit cross-compiled CI jobs on Debian Buster
Since the forced removal of gcc:sid:i386 in 0aacabc6, we lacked a 32-bit environment to build and test BIND 9 in the CI. gcc:buster:amd64cross32 adds an environment to cross-compile BIND 9 to 32-bits on Debian Buster amd64 image with 32-bit BIND 9 dependencies. Commit also adds sanity checks to ensure that compiled objects are not of the build platform triplet type.
(cherry picked from commit bfcaa2a8)