find boot files relative to executable by default #81

Job	Run time
ci (tpb, ubuntu-22.04, --pb --threads --enable-libffi, test-some-fast)	31m 11s
ci (a6osx, macos-12)	16m 44s
ci (ta6osx, macos-12)	22m 4s
ci (i3le, ubuntu-22.04)	13m 15s
ci (ti3le, ubuntu-22.04)	16m 3s
ci (a6le, ubuntu-22.04)	9m 14s
ci (ta6le, ubuntu-22.04)	12m 12s
ci (ta6le, ubuntu-22.04, reboot, -m=ta6le --force, re.boot SCHEME="chezscheme", test-some-fast)	8m 25s
ci (i3nt, windows-2022, vs)	12m 30s
ci (ti3nt, windows-2022, vs)	15m 23s
ci (a6nt, windows-2022, vs)	13m 14s
ci (ta6nt, windows-2022, vs)	15m 59s
ci (ta6nt, windows-2022, gcc)	13m 4s
	3h 19m 18s

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