configure.ac: In _Noreturn check, include <stdlib.h> for exit

Otherwise, an implicit functiona declaration is used, causing
a C99 compatibility issue.

Submitted upstream:

<https://lore.kernel.org/linux-modules/877cyq6kh9.fsf@oldenburg.str.redhat.com/>

diff --git a/configure b/configure
index d053310a8b4a313a..ec1f12d02428f848 100755
--- a/configure
+++ b/configure
@@ -14021,7 +14021,8 @@ rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
 printf %s "checking whether _Noreturn is supported... " >&6; }
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
-_Noreturn int foo(void) { exit(0); }
+#include <stdlib.h>
+	_Noreturn int foo(void) { exit(0); }
 _ACEOF
 if ac_fn_c_try_compile "$LINENO"
 then :
diff --git a/configure.ac b/configure.ac
index 6989e9360da23721..12e0518533201ccf 100644
--- a/configure.ac
+++ b/configure.ac
@@ -68,7 +68,8 @@ AC_COMPILE_IFELSE(
 
 AC_MSG_CHECKING([whether _Noreturn is supported])
 AC_COMPILE_IFELSE(
-	[AC_LANG_SOURCE([[_Noreturn int foo(void) { exit(0); }]])],
+	[AC_LANG_SOURCE([[#include <stdlib.h>
+	_Noreturn int foo(void) { exit(0); }]])],
         [AC_DEFINE([HAVE_NORETURN], [1], [Define if _Noreturn is available])
 	 AC_MSG_RESULT([yes])],
 	[AC_MSG_RESULT([no])])