Build failure with gcc 11.x on native_posix

[nashif]

Describe the bug
Warnings from new gcc turning into errors:

In file included from /home/nashif/Work/zephyrproject/zephyr/include/kernel_includes.h:39,
                 from /home/nashif/Work/zephyrproject/zephyr/include/kernel.h:17,
                 from /home/nashif/Work/zephyrproject/zephyr/include/zephyr.h:18,
                 from /home/nashif/Work/zephyrproject/zephyr/kernel/init.c:14:
/home/nashif/Work/zephyrproject/zephyr/include/sys/thread_stack.h:155:16: error: ignoring attribute ‘section (".noinit.\"WEST_TOPDIR/zephyr/kernel/init.c\".3")’ because it conflicts with previous ‘section (".noinit.\"WEST_TOPDIR/zephyr/kernel/include/kernel_internal.h\".0")’ [-Werror=attributes]
  155 |         struct z_thread_stack_element __kstackmem \
      |                ^~~~~~~~~~~~~~~~~~~~~~
/home/nashif/Work/zephyrproject/zephyr/kernel/init.c:61:1: note: in expansion of macro ‘K_KERNEL_STACK_ARRAY_DEFINE’
   61 | K_KERNEL_STACK_ARRAY_DEFINE(z_interrupt_stacks, CONFIG_MP_NUM_CPUS,
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/nashif/Work/zephyrproject/zephyr/kernel/include/kernel_internal.h:136:36: note: previous declaration here
  136 | extern K_KERNEL_STACK_ARRAY_DEFINE(z_interrupt_stacks, CONFIG_MP_NUM_CPUS,
      |                                    ^~~~~~~~~~~~~~~~~~
/home/nashif/Work/zephyrproject/zephyr/include/sys/thread_stack.h:157:17: note: in definition of macro ‘K_KERNEL_STACK_ARRAY_DEFINE’
  157 |                 sym[nmemb][Z_KERNEL_STACK_LEN(size)]
      |                 ^~~
cc1: all warnings being treated as errors
gmake[2]: *** [zephyr/kernel/CMakeFiles/kernel.dir/build.make:134: zephyr/kernel/CMakeFiles/kernel.dir/init.c.obj] Error
1
gmake[1]: *** [CMakeFiles/Makefile2:2781: zephyr/kernel/CMakeFiles/kernel.dir/all] Error 2
gmake: *** [Makefile:103: all] Error 2

To Reproduce

On fedora 34 with gcc 11.x

Steps to reproduce the behavior:

1. twister -T samples/philosophers/ -p native_posix
2. See error

[niflostancu]

I've encountered this as well with my projects (using the ARM Cortex-M arch) and I would like it fixed.

The actual cause is that there are many separate files defining the z_interrupt_stacks extern symbol:

• kernel/include/kernel_internal.h;
• other includes / modules declaring the same symbol (e.g., aarch32/cortex_m/stack.h);

Both use the K_KERNEL_STACK_ARRAY_DEFINE macro, which calls upon the __in_section_unique macro generating a unique section string for each filename it's used.
The real solution would be to have a single header file declaring symbols using these file-named sections.

As workaround, I use -Wno-attributes or -Wno-error=attributes (when -Werror is desired) in my project cmake script:

check_set_compiler_property(APPEND PROPERTY warning_base -Wno-attributes)

[dcpleung]

#35893 should fix this.