CI: faster with borg-dir/borg.exe, fixes #9236 #5364

Job	Run time
lint	7s
security	13s
asan_ubsan	6m 3s
vm_tests (freebsd, 14.3, FreeBSD, true, borg-freebsd-14-x86_64-gh)	21m 28s
vm_tests (haiku, r1beta5, Haiku, false)	13m 46s
vm_tests (netbsd, 10.1, NetBSD, false)	17m 28s
vm_tests (openbsd, 7.7, OpenBSD, false)	22m 23s
native_tests (ubuntu-22.04, 3.11, docs)	2m 14s
native_tests (ubuntu-22.04, 3.10, mypy)	2m 15s
native_tests (ubuntu-22.04, 3.10, py310-llfuse)	2m 29s
native_tests (ubuntu-24.04, 3.14, py314-mfusepy)	2m 18s
windows_tests	0s
	1h 30m 44s

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