Remove ATOMIC_VAR_INIT

[sloretz]

Description

This fixes a new compile error on Ubuntu Resolute. The ATOMIC_VAR_INIT macro was deprecated in C17 and removed in C23. Lyrical targets C17, so I'm not 100% sure why the macro dissapeared. My best guess is CMake decided C23 "satisfies" the requirement for C17 features, and is using that.

In file included from /workspaces/lyrical/src/ros2/rcutils/src/filesystem.c:42:
/workspaces/lyrical/src/ros2/rcutils/src/filesystem.c: In function ‘rcutils_dir_iter_next’:
/workspaces/lyrical/src/ros2/rcutils/src/filesystem.c:478:67: warning: statement with no effect [-Wunused-value]
  478 |   RCUTILS_CHECK_FOR_NULL_WITH_MSG(iter->state, "iter is invalid", false);
      |                                                                   ^~~~~
/workspaces/lyrical/src/ros2/rcutils/include/rcutils/error_handling.h:215:7: note: in definition of macro ‘RCUTILS_CHECK_FOR_NULL_WITH_MSG’
  215 |       error_statement; \
      |       ^~~~~~~~~~~~~~~
/workspaces/lyrical/src/ros2/rcutils/src/testing/fault_injection.c:19:63: error: implicit declaration of function ‘ATOMIC_VAR_INIT’; did you mean ‘ATOMIC_FLAG_INIT’? [-Wimplicit-function-declaration]
   19 | static atomic_int_least64_t g_rcutils_fault_injection_count = ATOMIC_VAR_INIT(-1);
      |                                                               ^~~~~~~~~~~~~~~
      |                                                               ATOMIC_FLAG_INIT
/workspaces/lyrical/src/ros2/rcutils/src/testing/fault_injection.c:19:63: error: initializer element is not constant
gmake[2]: *** [CMakeFiles/rcutils.dir/build.make:443: CMakeFiles/rcutils.dir/src/testing/fault_injection.c.o] Error 1
gmake[2]: *** Waiting for unfinished jobs....
gmake[1]: *** [CMakeFiles/Makefile2:294: CMakeFiles/rcutils.dir/all] Error 2
gmake: *** [Makefile:146: all] Error 2

Is this user-facing behavior change?

no

Did you use Generative AI?

I used gemini to research the replacement

Additional Information

Docs that talk about why ATOMIC_VAR_INIT is replaced with normal initialization: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2886.htm

[sloretz]

CI (testing just rcutils)

• Linux
• Linux-aarch64
• Linux-rhel
• Windows

[sloretz]

CI Attempt 2 with hopefully a fix for Windows

• Linux
• Linux-aarch64
• Linux-rhel
• Windows

[fujitatomoya]

this replaces #554 (i actually think that this PR is the correct), and closes #554

[fujitatomoya]

correction, this closes #553