Tools: use /usr/bin/env to find python3 #42917

Job	Run time
build (stm32f7, chibios, 10)	5m 35s
build (stm32h7, chibios, 10)	5m 19s
build (fmuv2-plane, chibios, 10)	3m 49s
build (periph-build, chibios, 10)	5m 23s
build (iofirmware, chibios, 10)	3m 27s
build (CubeOrange-bootloader, chibios, 10)	3m 0s
build (fmuv3-bootloader, chibios, 10)	2m 55s
build (revo-bootloader, chibios, 10)	3m 11s
build (stm32h7-debug, chibios, 10)	4m 40s
build (fmuv3, chibios, 10)	7m 20s
build (revo-mini, chibios, 10)	6m 9s
build (MatekF405-Wing, chibios, 10)	6m 44s
build (CubeOrange-ODID, chibios, 10)	4m 46s
build (CubeRedPrimary-bootloader, chibios, 10)	2m 56s
build (configure-all, chibios, 10)	12m 36s
build (build-options-defaults-test, chibios, 10)	8m 48s
build (signing, chibios, 10)	4m 35s
build (CubeOrange-PPP, chibios, 10)	4m 1s
build (CubeRed-EKF2, chibios, 10)	4m 0s
build (SOHW, chibios, 10)	5m 18s
build (Pixhawk6X-PPPGW, chibios, 10)	3m 32s
build (new-check, chibios, 10)	6m 15s
	1h 54m 19s

Provide feedback