tools: flash-full.sh add hint about tweaks in comment

The build + flash is already long, so initializing esp-idf inline in a
catch-all update from git script - as well as even wiping the build state
can be useful.

tools/flash-full.sh

@@ -9,6 +9,15 @@ if [ ! -f sdkconfig.defaults ] || [ ! -f recovery/sdkconfig.defaults ]; then
     exit 1
 fi
 
+# Uncomment the following and adapt the path to make this script also
+# initialize esp-idf:
+#
+#source ~/esp-idf/export.sh
+
+# and the following to ensure a clean build
+#
+#rm -rf build sdkconfig
+
 idf.py build erase_flash
 ( cd recovery ; idf.py build flash )
 idf.py app-flash