添加rtthread相关代码

riscv/rtthread/components/utilities/ymodem/SConscript

@@ -0,0 +1,15 @@
+from building import *
+
+cwd     = GetCurrentDir()
+src     = Split('''
+ymodem.c
+''')
+
+CPPPATH = [cwd]
+
+if GetDepend('YMODEM_USING_FILE_TRANSFER'):
+    src += ['ry_sy.c']
+
+group   = DefineGroup('Utilities', src, depend = ['RT_USING_RYM'], CPPPATH = CPPPATH)
+
+Return('group')