Update nix-tooling.md #471

Job	Run time
build-f3discovery-doc	1m 12s
build-book	3m 56s
build-microbit-chapter (05-led-roulette)	32s
build-f3discovery-chapter (05-led-roulette)	30s
build-microbit-chapter (07-uart)	29s
build-microbit-doc	2m 12s
build-f3discovery-chapter (06-hello-world)	27s
build-microbit-chapter (08-i2c)	39s
build-f3discovery-chapter (07-registers)	33s
build-microbit-chapter (09-led-compass)	43s
build-f3discovery-chapter (08-leds-again)	33s
build-microbit-chapter (10-punch-o-meter)	40s
build-f3discovery-chapter (09-clocks-and-timers)	24s
build-f3discovery-chapter (11-usart)	28s
build-f3discovery-chapter (14-i2c)	34s
build-f3discovery-chapter (15-led-compass)	22s
build-f3discovery-chapter (16-punch-o-meter)	29s
	14m 43s

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