libgcc: Remove useless forward declaration [PR121397]

libgcc: Remove useless forward declaration [PR121397]

aarch64 for some strange reason unconditionally enables -Werror for libgcc
building and this particular file for some strange reason contains
a useless static forward declaration of a function only defined in the
  #if defined __sun__ && defined __svr4__
block and not otherwise (with __attribute__((constructor))).
And we warn (with -Werror error) in the non-__sun__/__svr4__ case because
it declares a static function that is never defined.
The forward declaration makes no sense to me, for static functions
forward declarations shouldn't be needed even for -Wstrict-prototypes,
and AFAIK we don't warn on static __attribute__((constructor)) void foo (void) {}
being unused.  And the function isn't used before being defined.

So, the following patch just removes the forward declaration.

2025-08-06  Jakub Jelinek  <jakub@redhat.com>

	PR libgcc/121397
	* enable-execute-stack-mprotect.c (check_enabling): Remove useless
	forward declaration.