Support portable boot files on more platforms #57

Job	Run time
ci (tpb, ubuntu-22.04, --pb --threads --enable-libffi, test-some-fast)	30m 8s
ci (a6osx, macos-12)	20m 39s
ci (ta6osx, macos-12)	28m 0s
ci (i3le, ubuntu-22.04)	11m 42s
ci (ti3le, ubuntu-22.04)	20m 41s
ci (a6le, ubuntu-22.04)	9m 17s
ci (ta6le, ubuntu-22.04)	22m 33s
ci (ta6le, ubuntu-22.04, reboot, -m=ta6le --force, re.boot SCHEME="chezscheme", test-some-fast)	8m 21s
ci (i3nt, windows-2022, vs)	21m 12s
ci (ti3nt, windows-2022, vs)	14m 38s
ci (a6nt, windows-2022, vs)	20m 37s
ci (ta6nt, windows-2022, vs)	15m 56s
ci (ta6nt, windows-2022, gcc)	13m 29s
	3h 57m 13s

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