Already in upstream via:

  <https://trac.sagemath.org/ticket/30494>
  <https://gitlab.inria.fr/gf2x/gf2x/-/commit/a2f0fd388c12ca0b9f4525c6cfbc515418dcbaf8>

--- gf2x-gf2x-1.3.0/config/acinclude.m4.orig	2019-12-10 06:35:45.000000000 -0700
+++ gf2x-gf2x-1.3.0/config/acinclude.m4	2022-11-23 19:59:12.706926961 -0700
@@ -661,6 +661,7 @@ AC_DEFUN([GF2X_PROG_CC_FOR_BUILD_WORKS],
 # remove anything that might look like compiler output to our "||" expression
 rm -f conftest* a.out b.out a.exe a_out.exe
 cat >conftest.c <<EOF
+#include <stdlib.h>
 int
 main ()
 {
@@ -699,6 +700,7 @@ AC_DEFUN([GF2X_PROG_EXEEXT_FOR_BUILD],
 AC_CACHE_CHECK([for build system executable suffix],
                gf2x_cv_prog_exeext_for_build,
 [cat >conftest.c <<EOF
+#include <stdlib.h>
 int
 main ()
 {