添加rtthread相关代码

riscv/rtthread/components/drivers/fdt/SConscript

@@ -0,0 +1,16 @@
+# RT-Thread building script for bridge
+
+import os
+from building import *
+
+cwd = GetCurrentDir()
+objs = []
+list = os.listdir(cwd)
+
+if GetDepend('RT_USING_FDT'):
+    for d in list:
+        path = os.path.join(cwd, d)
+        if os.path.isfile(os.path.join(path, 'SConscript')):
+            objs = objs + SConscript(os.path.join(d, 'SConscript'))
+
+Return('objs')