Building from source with BOARD=PICO_R1_3

I am trying to build the new pico firmware from source.

I have soldered jumpers from the BTN / BOOT0 pads so I can quickly change chip modes.

I edited ./boards/PICO_R1_3.py so that the libraries included are as follows:

'build' : {
   ...
   'libraries' : [
     'USB_HID',
     'NET',
     # 'GRAPHICS',
     # 'TV',
     'FILESYSTEM',
     'CRYPTO','SHA256','SHA512',
     # 'TLS',
     'NEOPIXEL'
   ],

Then I ran:

source scripts/provision.sh PICO_R1_3
make clean && BOARD=PICO_R1_3 DFU_UPDATE_BUILD=1 make
sudo dfu-util -a 0 -s 0x08000000 -D espruino_2v08.5_pico_1r3.bin

When I plug the pico into USB again without holding the button and without the aforementioned jumpers connected, the usual single red LED blink doesn't happen and it doesn't accept the following:

echo "digitalWrite(LED1,1);" >> /dev/ttyACM0

EDIT******

picocom --baud 9600 --flow n /dev/ttyACM0

allows me to interface with the espruino in the same way the WebIDE would. I am trying to use all free software on the command line. My main problem is the binary that is made by the make command doesn't provide a TTY on the /dev/ttyACM0 device as is normally provided on the official binary. I'm a free software purist and want to use only the basic tools.
*** end edit

Is there something missing in my strategy?

When I flash the official release firmware .bin file, it works fine.