libc: fix build in C23 mode

I would like to request a backport of the following C23 fix in order to fix the following QEMU build issue on Fedora 42:

In file included from qemu/tests/tcg/multiarch/system/memory.c:16:
qemu/roms/SLOF/lib/libc/include/stdbool.h:17:16: error: cannot use keyword ‘false’ as enumeration constant
   17 | typedef enum { false = 0, true } bool;
      |                ^~~~~

---

commit 277e043bde619c98beddf3d1c6780bc40cd2186d upstream.

GCC 15 defaults to C23, in which bool, true, and false are keywords.

Signed-off-by: Yaakov Selkowitz <yselkowi@redhat.com>
Message-ID: <20250419114403.879376-1-yselkowi@redhat.com>
Tested-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>