Support portable boot files on more platforms #63

Job	Run time
ci (tpb, ubuntu-22.04, --pb --threads --enable-libffi, test-some-fast)	29m 56s
ci (a6osx, macos-12)	19m 25s
ci (ta6osx, macos-12)	20m 10s
ci (i3le, ubuntu-22.04)	15m 47s
ci (ti3le, ubuntu-22.04)	24m 32s
ci (a6le, ubuntu-22.04)	13m 31s
ci (ta6le, ubuntu-22.04)	13m 26s
ci (ta6le, ubuntu-22.04, reboot, -m=ta6le --force, re.boot SCHEME="chezscheme", test-some-fast)	8m 33s
ci (i3nt, windows-2022, vs)	11m 51s
ci (ti3nt, windows-2022, vs)	15m 17s
ci (a6nt, windows-2022, vs)	13m 2s
ci (ta6nt, windows-2022, vs)	25m 15s
ci (ta6nt, windows-2022, gcc)	20m 40s
	3h 51m 25s

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