posix:fpu: Enabling CONFIG_FPU and CONFIG_FPU_SHARING causes compiler error

[allemanm]

Describe the bug
When I build the hello_world sample for native_sim with CONFIG_FPU and CONFIG_FPU_SHARING enabled, the compiler throws an error. I am checked out on Zephyr 53738cf92479610bcf79fe738636a2b920224a36.

To Reproduce
Run the following command:
west build samples/hello_world -b native_sim -p -- -DCONFIG_FPU=y -DCONFIG_FPU_SHARING=y

Expected behavior
I would expect it to build successfully.

Logs and console output
Compiler output:

FAILED: zephyr/CMakeFiles/native_runner_executable zephyr/zephyr.exe /home/project/zephyr/build/zephyr/CMakeFiles/native_runner_executable /home/project/zephyr/build/zephyr/zephyr.exe 
cd /home/project/zephyr/build/zephyr && /usr/bin/make -f /home/project/zephyr/scripts/native_simulator/Makefile all --warn-undefined-variables -r NSI_CONFIG_FILE=/home/project/zephyr/build/zephyr/NSI/nsi_config
/usr/bin/ld: /home/project/zephyr/build/zephyr/NSI/home/project/zephyr/build/zephyr/zephyr.elf.loc_cpusw.o: in function `halt_thread':
/home/project/zephyr/kernel/sched.c:1372: undefined reference to `arch_float_disable'
collect2: error: ld returned 1 exit status
make: *** [/home/project/zephyr/scripts/native_simulator/Makefile:131: /home/project/zephyr/build/zephyr/zephyr.exe] Error 1
ninja: build stopped: subcommand failed.
FATAL ERROR: command exited with status 1: /usr/bin/cmake --build /home/project/zephyr/build

Additional context
I added the following to zephyr/arch/posix/core/thread.c but I am not sure if this is correct.

#if defined(CONFIG_FPU) && defined(CONFIG_FPU_SHARING)
int arch_float_disable(struct k_thread *thread)
{
	/* Posix always has FPU enabled so cannot be disabled */
	return -ENOTSUP;
}

int arch_float_enable(struct k_thread *thread, unsigned int options)
{
	/* Posix always has FPU enabled so nothing to do here */
	return 0;
}
#endif /* CONFIG_FPU && CONFIG_FPU_SHARING */

[aescolar]

@allemanm do you want to submit a PR?