[PATCH] Include stdlib.h as necessary in configure checks

[Saagar Jha <saagar@saagarjha.com>]

exit(3) needs it, and without it the checks fail on macOS. This causes
zsh to hang because it thinks those things are broken and tries to
employ unnecessary (and in this case incorrect) workarounds.
---
 configure.ac | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/configure.ac b/configure.ac
index 995f010b9..906c174ed 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2264,6 +2264,7 @@ zsh_cv_sys_killesrch,
 [AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #include <unistd.h>
 #include <signal.h>
+#include <stdlib.h>
 #include <errno.h>
 main()
 {
@@ -2289,6 +2290,7 @@ if test x$signals_style = xPOSIX_SIGNALS; then
     zsh_cv_sys_sigsuspend,
     [AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #include <signal.h>
+#include <stdlib.h>
 #include <unistd.h>
 int child=0;
 void handler(sig)
-- 
2.28.0