Support portable boot files on more platforms #10

Job	Run time
ci (tpb, ubuntu-22.04, --pb --threads --enable-libffi, test-some-fast)	43m 45s
ci (a6osx, macos-12)	52s
ci (ta6osx, macos-12)	54s
ci (i3le, ubuntu-22.04)	18m 24s
ci (ti3le, ubuntu-22.04)	23m 48s
ci (a6le, ubuntu-22.04)	13m 41s
ci (ta6le, ubuntu-22.04)	17m 32s
ci (ta6le, ubuntu-22.04, reboot, -m=ta6le --force, re.boot SCHEME="chezscheme", test-some-fast)	14m 33s
ci (i3nt, windows-2022, vs)	33m 42s
ci (ti3nt, windows-2022, vs)	36m 37s
ci (a6nt, windows-2022, vs)	27m 57s
ci (ta6nt, windows-2022, vs)	34m 36s
ci (ta6nt, windows-2022, gcc)	20m 2s
	4h 46m 23s

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