Update pio_start.txt

Author: Jason2866

configs/pio_start.txt

@@ -24,6 +24,7 @@ http://arduino.cc/en/Reference/HomePage
 
 # Extends: https://github.com/jason2866/platform-espressif32/blob/develop/builder/main.py
 
+import platform
 from os.path import basename, join
 
 from SCons.Script import DefaultEnvironment