fix option check.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@664 bbd45198-f89e-11dd-88c7-29a3b14d5316

components/dfs/SConscript

@@ -52,17 +52,16 @@ src_local = dfs
 # The set of source files associated with this SConscript file.
 path = [RTT_ROOT + '/components/dfs', RTT_ROOT + '/components/dfs/include']
 
-if rtconfig.RT_USING_DFS_YAFFS2:
+if 'RT_USING_DFS_YAFFS2' in dir(rtconfig) and rtconfig.RT_USING_DFS_YAFFS2:
     src_local = src_local + yaffs2_main + yaffs2_comm
     path = path + [RTT_ROOT + '/components/dfs/filesystems/yaffs2', RTT_ROOT + '/components/dfs/filesystems/yaffs2/direct']
 
-if rtconfig.RT_DFS_ELM_USE_LFN:
+if 'RT_DFS_ELM_USE_LFN' in dir(rtconfig) and rtconfig.RT_DFS_ELM_USE_LFN:
     elmfat += ['filesystems/elmfat/option/cc936.c']
 
-if rtconfig.RT_USING_DFS_ELMFAT:
+if 'RT_USING_DFS_ELMFAT' in dir(rtconfig) and rtconfig.RT_USING_DFS_ELMFAT:
     src_local = src_local + elmfat
-    # path = path + [RTT_ROOT + '/components/dfs/filesystems/elmfat']
-		
+
 # group definitions
 group = {}
 group['name'] = 'Filesystem'