toolchain: fix mkdir invocation #402

Job	Run time
call-ci / build (armv7a7-imx6ull-evk)	1m 30s
call-ci / build (armv7a9-zynq7000-qemu)	1m 57s
call-ci / build (armv7a9-zynq7000-zedboard)	1m 33s
call-ci / build (armv7a9-zynq7000-zturn)	1m 38s
call-ci / build (armv7m4-stm32l4x6-nucleo)	1m 25s
call-ci / build (armv7m7-imxrt105x-evk)	1m 40s
call-ci / build (armv7m7-imxrt106x-evk)	1m 33s
call-ci / build (armv7m7-imxrt117x-evk)	1m 44s
call-ci / build (host-generic-pc)	1m 28s
call-ci / build (ia32-generic-pc)	1m 39s
call-ci / build (ia32-generic-qemu)	1m 19s
call-ci / build (riscv64-generic-qemu)	1m 8s
call-ci / build (riscv64-generic-spike)	1m 8s
call-ci / test EMU (armv7a9-zynq7000-qemu)	7m 52s
call-ci / test EMU (host-generic-pc)	1m 6s
call-ci / test EMU (ia32-generic-qemu)	4m 49s
call-ci / test HW (armv7a7-imx6ull-evk)	3m 53s
call-ci / test HW (armv7m7-imxrt106x-evk)	1m 43s
call-ci / test HW (armv7m7-imxrt117x-evk)	2m 21s
call-ci / test HW (armv7a9-zynq7000-zedboard)	4m 54s
call-ci / test HW (armv7m4-stm32l4x6-nucleo)	9m 22s
call-ci / tests-summary	42s
call-ci / send-notification	0s
call-ci / notify ci team using e-mail	0s
	56m 24s

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