How to (cross) compile a 32bit native_posix app for RaspberryPi (armv71)?

[CSparn]

Hi,

I would like to compile the mesh_shell app from /tests/bluetooth/mesh_shell as a native_posix(32bit) app for the RaspberryPi(armv71). I'm looking for a solution for some days now, but I could not find one that is working.
I tried to compile it in 2 ways:

1. Cross compiling the app on an Ubuntu (x86_64) system. For that I installed an arm gcc like described here:
   https://docs.zephyrproject.org/latest/getting_started/toolchain_other_x_compilers.html
   and set the Variables: ZEPHYR_TOOLCHAIN_VARIANT and CROSS_COMPILE
   But when I run:

west build -b native_posix tests/bluetooth/mesh_shell`

the host-gcc (x86) is used. What options do I have to set additionally to cross compile for arm?

2. The second option I tried is "natively" compiling the native_posix app on the RaspberryPi. But when I try to run the compilation, I always get the compiling error:

gcc: error: unrecognized command line option '-m32'; did you mean '-mbe32'? ninja: build stopped: subcommand failed. FATAL ERROR: command exited with status 1: /usr/bin/cmake --build /opt/zephyrproject/zephyr/build

Of course this is because the option -m32 is for the x86 gcc, but I don't know what options I have to set instead. And removing the -m32 option is also leading to errors. Does anyone know how to set the right options?

I could find thses posts that describe this problem and like I think a solution for aarch64
#24843
, but I don't understand what I have to do to get it working for my scenario.
Are there maybe some CONFIGS in prf.conf missing, or do I have to change the cmake options?

Thanks in advance
Greetings
CSparn