bash: use -std=gnu17 also for native CFLAGS

* fixes builds on host with gcc-15:
  http://errors.yoctoproject.org/Errors/Details/853016/

../../bash-5.2.37/builtins/mkbuiltins.c:268:29: error: too many arguments to function ‘xmalloc’; expected 0, have 1
  268 |           error_directory = xmalloc (2 + strlen (argv[arg_index]));
      |                             ^~~~~~~  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

(From OE-Core rev: 55c144bd17665f70cd15e36f3405f502a962f039)

Signed-off-by: Martin Jansa <martin.jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

meta/recipes-extended/bash/bash_5.2.21.bb

@@ -23,5 +23,8 @@ DEBUG_OPTIMIZATION:append:armv4 = " ${@bb.utils.contains('TUNE_CCARGS', '-mthumb
 DEBUG_OPTIMIZATION:append:armv5 = " ${@bb.utils.contains('TUNE_CCARGS', '-mthumb', '-fomit-frame-pointer', '', d)}"
 
 CFLAGS += "-std=gnu17"
+# mkbuiltins.c is built with native toolchain and needs gnu17 as well:
+# http://errors.yoctoproject.org/Errors/Details/853016/
+BUILD_CFLAGS += "-std=gnu17"
 
 BBCLASSEXTEND = "nativesdk"