Makefile: sort boards in usage text alphabetically

Makefile

@@ -13,20 +13,20 @@ usage:
 	@echo
 	@echo "The next step is to choose a board to build Tock for. Mainline"
 	@echo "libtock-rs currently includes support for the following platforms:"
+	@echo " - apollo3"
+	@echo " - clue_nrf52840"
+	@echo " - esp32_c3_devkitm_1"
 	@echo " - hail"
-	@echo " - nrf52840"
+	@echo " - hifive1"
+	@echo " - imxrt1050"
 	@echo " - microbit_v2"
+	@echo " - nrf52"
+	@echo " - nrf52840"
 	@echo " - nucleo_f429zi"
 	@echo " - nucleo_f446re"
 	@echo " - opentitan"
-	@echo " - hifive1"
-	@echo " - nrf52"
-	@echo " - imxrt1050"
-	@echo " - apollo3"
 	@echo " - stm32f3discovery"
 	@echo " - stm32f412gdiscovery"
-	@echo " - esp32_c3_devkitm_1"
-	@echo " - clue_nrf52840"
 	@echo
 	@echo "Run 'make setup' to setup Rust to build libtock-rs."
 	@echo "Run 'make <board> EXAMPLE=<>' to build EXAMPLE for that board."