closes bpo-13497: Fix `broken nice` configure test. (GH-12041)
Per POSIX, `nice(3)` requires `unistd.h` and `exit(3)` requires `stdlib.h`.
Fixing the test will prevent false positives with pedantic compilers like clang.
diff --git a/configure.ac b/configure.ac
index bb7861b..c7380ca 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4727,6 +4727,8 @@
AC_MSG_CHECKING(for broken nice())
AC_CACHE_VAL(ac_cv_broken_nice, [
AC_RUN_IFELSE([AC_LANG_SOURCE([[
+#include <stdlib.h>
+#include <unistd.h>
int main()
{
int val1 = nice(1);