update docs

Author: dingo35

docs/building_flashing.md

@@ -12,6 +12,16 @@ cd SmartEVSE-3.5/SmartEVSE
 pio run
 ```
 
+To enable the telnet server that allows you to online view the debug logs, add the compile flag like this:
+```
+PLATFORMIO_BUILD_FLAGS='-DDBG=1' pio run
+```
+
+Other compile flags:
+* DDBG=0 : no logging (default)
+* DDBG=2 : log via USB-C connector
+* DMIN_CURRENT=5 ; decrease minimum allowed current from 6A to 5A ----> THIS IS NOT FOLLOWING THE PROTOCOLS SO AT YOUR OWN RISK !!!
+
 For versions older than v3.6.0, build the spiffs filesystem:
 * Compile spiffs.bin: `pio run -t buildfs`