added a basic mutex based on a waitable #413

Job	Run time
Build each header individually	56s
build (atsam3x8e)	20s
build (atsam4s2b)	20s
build (lpc1756)	20s
build (lpc802)	20s
build (lpc1754)	12s
build (stm32h723)	14s
build (lpc1788)	14s
build (lpc1759)	16s
build (max32625)	19s
build (lpc55s66)	23s
build (stm32f103)	19s
build (max32660)	20s
build (rp2350)	11s
build (lpc1752)	23s
build (mb9bf566k)	21s
build (stm32f407)	23s
build (tmpm373)	24s
	6m 15s

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