Fix: semihosting cleanup #1888

Job	Run time
build-mingw (windows-2022, ucrt64)	2m 29s
build-linux (ubuntu-20.04, focal, clang-15, 12.2.Rel1)	3m 38s
build-mingw (windows-2022, clang64)	2m 17s
build-linux (ubuntu-20.04, focal, gcc-11, 12.2.Rel1)	3m 33s
build-linux (focal, 96b_carbon	41s
size-diff	44s
build-linux (focal, bluepill	31s
build-linux (focal, f072	34s
build-linux (focal, f3	35s
build-linux (focal, f4discovery	39s
build-linux (focal, hydrabus	33s
build-linux (focal, launchpad-icdi	34s
build-linux (focal, native	34s
build-linux (focal, stlink	35s
build-linux (focal, stlinkv3	38s
build-linux (focal, swlink	33s
	19m 8s

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