travis: Build esp32 firmware as part of Travis CI.
travis: Build esp32 firmware as part of Travis CI.

Toolchain installation and build takes about 3 minutes.

pfalcon/micropython,henriknelson/micropython,trezor/micropython,trezor/micropython,bvernoux/micropython,bvernoux/micropython,tobbad/micropython,adafruit/circuitpython,kerneltask/micropython,kerneltask/micropython,MrSurly/micropython,tobbad/micropython,selste/micropython,selste/micropython,adafruit/circuitpython,pozetroninc/micropython,bvernoux/micropython,pozetroninc/micropython,MrSurly/micropython,pfalcon/micropython,pozetroninc/micropython,trezor/micropython,selste/micropython,trezor/micropython,pramasoul/micropython,bvernoux/micropython,kerneltask/micropython,tobbad/micropython,MrSurly/micropython,MrSurly/micropython,pramasoul/micropython,MrSurly/micropython,pramasoul/micropython,pozetroninc/micropython,selste/micropython,kerneltask/micropython,adafruit/circuitpython,henriknelson/micropython,adafruit/circuitpython,kerneltask/micropython,selste/micropython,pramasoul/micropython,bvernoux/micropython,adafruit/circuitpython,tobbad/micropython,pfalcon/micropython,pfalcon/micropython,tobbad/micropython,henriknelson/micropython,pramasoul/micropython,trezor/micropython,henriknelson/micropython,adafruit/circuitpython,pfalcon/micropython,pozetroninc/micropython,henriknelson/micropython