[BSP] [ci skip] fix list issue in SConscript

bsp/xplorer4330/m4/SConscript

@@ -2,11 +2,11 @@ from building import *
 
 cwd  = GetCurrentDir()
 objs = []
-list = os.listdir(cwd+'\\..')
+list = os.listdir(os.path.join(cwd, '..'))
 
 for d in list:
     if d!='m4':
-        path = os.path.join(cwd+'\\..', d)
+        path = os.path.join(cwd, '..', d)
         if os.path.isfile(os.path.join(path, 'SConscript')):
             objs = objs + SConscript(os.path.join(path, 'SConscript'))