[PATCH] getcwd: fix compile error in configure check

[Pádraig Brady]

I pushed this to fix a compile error in the getcwd configure check.

diff --git a/m4/getcwd-abort-bug.m4 b/m4/getcwd-abort-bug.m4
index 9b3b563..544b037 100644
--- a/m4/getcwd-abort-bug.m4
+++ b/m4/getcwd-abort-bug.m4
@@ -27,6 +27,7 @@ AC_DEFUN([gl_FUNC_GETCWD_ABORT_BUG],
      AC_RUN_IFELSE(
        [AC_LANG_SOURCE(
           [[
+#include <errno.h>
 #include <stdlib.h>
 #if HAVE_UNISTD_H
 # include <unistd.h>