Dyson

This affect gobject-introspection which uses ldd during the build:

$ fakeroot ldd /usr/bin/bash
ldd: /usr/bin/bash: ELF class: ELFCLASS64: is incompatible with 32-bit system

$ ldd /usr/bin/bash
        libncurses.so.5 =>       /lib/x86_64-illumos/libncurses.so.5
        libtinfo.so.5 =>         /lib/x86_64-illumos/libtinfo.so.5
        libc.so.1 =>     /lib/x86_64-illumos/libc.so.1
        libsocket.so.1 =>        /lib/x86_64-illumos/libsocket.so.1
        libiconv.so.2 =>         /lib/x86_64-illumos/libiconv.so.2
        libgcc_s.so.1 =>         /lib/x86_64-illumos/libgcc_s.so.1
        libnsl.so.1 =>   /lib/x86_64-illumos/libnsl.so.1
        libmp.so.2 =>    /lib/x86_64-illumos/libmp.so.2
        libmd.so.1 =>    /lib/x86_64-illumos/libmd.so.1
        libm.so.2 =>     /lib/x86_64-illumos/libm.so.2

Some hints:

$ fakeroot bash -c 'export'
...
declare -x LD_LIBRARY_PATH="/usr/lib/x86_64-illumos:/usr/lib64/libfakeroot:/usr/lib32/libfakeroot" 
declare -x LD_PRELOAD="libfakeroot-sysv.so" 
...

Then:

$ LD_PRELOAD="libfakeroot-sysv.so"  ldd /usr/bin/bash
ldd: /usr/bin/bash: ELF class: ELFCLASS64: is incompatible with 32-bit system

$ LD_PRELOAD_64="libfakeroot-sysv.so"  ldd /usr/bin/bash
ldd: /usr/bin/bash: ELF class: ELFCLASS64: is incompatible with 32-bit system