Missing system inlude in self-defined autoconf tests
https://bugs.gentoo.org/908483
--- a/m4macros/eso.m4
+++ b/m4macros/eso.m4
@@ -252,6 +252,7 @@
                        AC_RUN_IFELSE([
 #include <stdio.h>
 #include <stdarg.h>
+#include <stdlib.h>
 
 int
 doit(char * s, ...)
@@ -701,6 +702,7 @@
                    [
                        AC_RUN_IFELSE([
 #include <stdarg.h>
+#include <stdlib.h>
 
 void f(int i, ...)
 {
@@ -733,6 +735,7 @@
                    [
                        AC_RUN_IFELSE([
 #include <stdarg.h>
+#include <stdlib.h>
 
 void f(int i, ...)
 {
@@ -784,6 +787,7 @@
                    [
                        AC_RUN_IFELSE([
 #include <stdarg.h>
+#include <stdlib.h>
 
 void f(int i, ...)
 {