fix: memory leak: buf #1185

Job	Run time
build-arm (imxrt)	4m 47s
build-arm (kinetis_k kinetis_kl)	1m 39s
build-arm (lpc17 lpc18 lpc40 lpc43)	2m 46s
build-arm (lpc54 lpc55)	2m 59s
build-arm (mcx)	1m 43s
build-arm (nrf)	4m 0s
build-arm (ra)	3m 1s
build-arm (rp2040)	2m 5s
build-arm (samd21)	3m 17s
build-arm (samd51)	2m 3s
build-arm (stm32f0)	1m 57s
build-arm (stm32f1)	1m 8s
build-arm (stm32f4)	3m 15s
build-arm (stm32f7)	2m 16s
build-arm (stm32g0)	55s
build-arm (stm32g4)	1m 28s
build-arm (stm32h5)	1m 33s
build-arm (stm32h7)	2m 53s
build-arm (stm32l4)	1m 57s
build-arm (stm32u5)	1m 26s
hil-test (feather_nrf52840_express)	47s
hil-test (itsybitsy_m4)	1m 8s
hil-test (raspberry_pi_pico)	42s
	49m 45s

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