Add support for the Urboot bootloader #144

Job	Run time
build (ubuntu-latest, examples/arduino-blink)	1m 31s
build (ubuntu-latest, examples/arduino-external-libs)	42s
build (ubuntu-latest, examples/arduino-internal-libs)	35s
build (ubuntu-latest, examples/arduino-own-src_dir)	29s
build (ubuntu-latest, examples/assembly-blink)	18s
build (ubuntu-latest, examples/digitstump-mouse)	31s
build (ubuntu-latest, examples/engduino-magnetometer)	33s
build (ubuntu-latest, examples/native-blink)	25s
build (windows-latest, examples/arduino-blink)	6m 43s
build (windows-latest, examples/arduino-external-libs)	1m 15s
build (windows-latest, examples/arduino-internal-libs)	1m 27s
build (windows-latest, examples/arduino-own-src_dir)	50s
build (windows-latest, examples/assembly-blink)	46s
build (windows-latest, examples/digitstump-mouse)	1m 4s
build (windows-latest, examples/engduino-magnetometer)	1m 16s
build (windows-latest, examples/native-blink)	1m 14s
build (macos-latest, examples/arduino-blink)	2m 34s
build (macos-latest, examples/arduino-external-libs)	1m 3s
build (macos-latest, examples/arduino-internal-libs)	1m 16s
build (macos-latest, examples/arduino-own-src_dir)	42s
build (macos-latest, examples/assembly-blink)	53s
build (macos-latest, examples/digitstump-mouse)	47s
build (macos-latest, examples/engduino-magnetometer)	59s
build (macos-latest, examples/native-blink)	28s
	28m 21s

Provide feedback