This commit adds support for building the esp32 port with cmake, and in
particular it builds MicroPython as a component within the ESP-IDF. Using
cmake and the ESP-IDF build infrastructure makes it much easier to maintain
the port, especially with the various new ESP32 MCUs and their required
toolchains.
Signed-off-by: Damien George <damien@micropython.org>
Damien George