Only use faccessat(3) if AT_EACCESS is defined.

Apparently Android (bionic) has faccessat() but not AT_EACCESS.
Bug #940.

src/sudo_edit.c

@@ -85,7 +85,7 @@ switch_user(uid_t euid, gid_t egid, int ngroups, GETGROUPS_T *groups)
     debug_return;
 }
 
-#ifdef HAVE_FACCESSAT
+#if defined(HAVE_FACCESSAT) && defined(AT_EACCESS)
 /*
  * Returns true if the open directory fd is owned or writable by the user.
  */
@@ -193,7 +193,7 @@ dir_is_writable(int dfd, struct user_details *ud, struct command_details *cd)
     errno = EACCES;
     debug_return_int(false);
 }
-#endif /* HAVE_FACCESSAT */
+#endif /* HAVE_FACCESSAT && AT_EACCESS */
 
 /*
  * Find our temporary directory, one of /var/tmp, /usr/tmp, or /tmp