cortexm: Probe imx before kinetis #470

Job	Run time
build-linux (ubuntu-20.04, focal, clang-9, 12.2.Rel1)	3m 11s
build-linux (ubuntu-20.04, focal, clang-15, 12.2.Rel1)	3m 16s
build-linux (ubuntu-20.04, focal, gcc-9, 12.2.Rel1)	3m 8s
build-mingw (windows-2019, mingw64)	8m 43s
build-linux (ubuntu-20.04, focal, gcc-11, 12.2.Rel1)	3m 42s
build-mingw (windows-2019, ucrt64)	11m 12s
build-linux (ubuntu-20.04, focal, gcc-9, 10-2020-q4)	3m 52s
build-mingw (windows-2019, clang64)	8m 4s
build-mingw (windows-2022, mingw64)	8m 58s
build-mingw (windows-2022, ucrt64)	8m 46s
build-mingw (windows-2022, clang64)	10m 38s
	1h 13m 30s

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