Compile 32-bit binaries in 32-bit packages
    
    Currently when .add_simple_compilation() is used, the resulting binary
    is always built for the architecture of the host, regardless of which
    arch the package is targetting.
    
    Full-on cross compilation is of course not possible, but at least for
    32-bit builds on a 64-bit host we can produce a 32-bit binary using
    gcc -m32.
    
    I am using this for multilib testing where I am producing both i386 and
    x86_64 packages and I want the file color to be correct in each package.