Test against the kernel the shipped tool installs, and stop the reaper eating the rootfs

[MayCXC]

Summary

Three things the integration suite needs before anything builds on it.

The kernel the tests fetch had drifted from the one users run. container installs kata 3.28.0 and its 6.18.15 kernel while these tests fetched 3.17.0, so the suite exercised a guest with a different feature set to the one it represents. Nested runtimes are the visible case: 3.17.0 was built without nf_tables, so a docker daemon inside a container fails there and works on what ships. Kata moved from xz to zstd between those releases, so the archive is no longer named for its compression, and tar is left to recognise it rather than being told, which also holds if the format changes again.

The reaper deleted the rootfs it meant to preserve. Running at a concurrency of one, it deletes everything in the test directory except the unpacked rootfs. It held that path as FileManager reports it, under /var, and compared it against contentsOfDirectory entries, which come back under /private/var, so the preserved path never matched and the rootfs went with the per-test files. The unpack coordinator still held it as unpacked, so the next test opened a rootfs that was no longer there. Both sides now resolve with resolvingSymlinksInPathWithPrivate, which exists for exactly this difference between two views of one directory.

make test says nothing about what it skipped. Tests guarded for Linux are compiled out on macOS, so the target reports success without running them, and the target that does run them is mentioned nowhere outside the makefile.

Motivation and Context

These are separable but all in the same area, and each is the kind of thing that makes a later failure hard to read: a guest with the wrong feature set, a test that fails because a previous test's cleanup removed its rootfs, and a green run that skipped what you cared about.

No issue filed, as this touches only the test suite and its docs and carries no user-visible behaviour. Happy to open one if the project prefers it recorded.

Testing

• swift build and make check clean.
• swift test: 603 tests in 83 suites passed.
• Integration suite runs against the kata release the config names, and the reaper no longer removes the shared rootfs between tests.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update