!467 修正切换scons版本(比如最新的4.3.0)后，编译时在"scons: Reading SConscript files ..."后打印出"b''的问题

Merge pull request !467 from 李润聪/gitee_master

tools/gcc.py

@@ -113,7 +113,7 @@ def GCCResult(rtconfig, str):
         stdout, stderr = child.communicate()
 
         # print(stdout)
-        if stderr != '':
+        if stderr != '' and stderr != b'':
             print(stderr)
 
         have_fdset = 0