configure: fix typo

configure.ac

@@ -1547,7 +1547,7 @@ then
     AC_MSG_ERROR([Could not find the LUA byte compiler.])
   ])
   AS_IF([test -d "${CONTRIB_DIR}" -a -f "${CONTRIB_DIR}/lib/liblua.a" -a `echo|${LUAC} -o - -|od -j 8 -N 2 -t x2|head -n 1|tr -s ' '|cut -d' ' -f2` != 0404], [
-    AC_MSG_ERROR([You need 32-bits luac when using using lua from contrib.])
+    AC_MSG_ERROR([You need 32-bits luac when using lua from contrib.])
   ])
 fi
 AM_CONDITIONAL(BUILD_LUA, [test "${have_lua}" = "yes"])