rm48x50: add GCC support

bsp/rm48x50/SConscript

@@ -0,0 +1,12 @@
+from building import *
+
+cwd  = GetCurrentDir()
+objs = []
+list = os.listdir(cwd)
+
+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')