[bsp] Update SConscript for stm32f429 apollo bsp

bsp/stm32f429-apollo/applications/SConscript

-Import('RTT_ROOT')
-Import('rtconfig')
 from building import *
 
-cwd     = os.path.join(str(Dir('#')), 'applications')
-#src	= Glob('*.c')
+cwd     = GetCurrentDir()
 CPPPATH = [cwd, str(Dir('#'))]
-
-src = Split("""
+src     = Split("""
 application.c
 startup.c
 """)
 
-# add gpio drivers.
+# add UI engine demo.
 if GetDepend('RT_USING_GUIENGINE'):
     src += ['rtgui_demo.c']
 
-
 group = DefineGroup('Applications', src, depend = [''], CPPPATH = CPPPATH)
 
 Return('group')

bsp/stm32f429-apollo/drivers/SConscript

-Import('RTT_ROOT')
-Import('rtconfig')
 from building import *
 
-cwd     = os.path.join(str(Dir('#')), 'drivers')
+cwd = GetCurrentDir()
 
 # add the general drivers.
 src = Split("""
@@ -15,7 +13,9 @@ drv_nand.c
 drv_mpu.c
 """)
 
-#drv_sdio_sd.c
+# add sdio driver
+if GetDepend('RT_USING_DFS'):
+    src += ['drv_sdio_sd.c']
 
 # add Ethernet drivers.
 if GetDepend('RT_USING_LWIP'):