emacs-29 121a9ff9f6: Fix alternate stack test in configure

[Eli Zaretskii]

branch: emacs-29
commit 121a9ff9f6fc69066ce30c2dbe6cbfbfdca6aeaa
Author: Florian Weimer <fweimer@redhat.com>
Commit: Eli Zaretskii <eliz@gnu.org>

    Fix alternate stack test in configure
    
    * configure.ac (emacs_cv_alternate_stack): Include <stdlib.h>
    for 'malloc's prototype.
---
 configure.ac | 1 +
 1 file changed, 1 insertion(+)

diff --git a/configure.ac b/configure.ac
index ac29f351fb..df19508d3d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5248,6 +5248,7 @@ AC_CACHE_CHECK([whether signals can be handled on 
alternate stack],
               [emacs_cv_alternate_stack],
   [AC_COMPILE_IFELSE(
      [AC_LANG_PROGRAM([[#include <signal.h>
+                       #include <stdlib.h>
                      ]],
                      [[stack_t ss;
                        struct sigaction sa;