A separate process is `spawnSync`'ed on process exit to cleanup
temporary directories, introduced in #13769 that followed up after
#13343.
A separate process might stall for various fs-related issues, which
prevents the original process from exiting.
With the recent changes, we always gracefully close and cleanup after
all launched executables before calling `process.exit()`, and so it
should only be possible to leave temp directories when using Playwright
and calling `process.exit()` programmatically without closing browsers.
We can now drop the extra process and rely on `rimraf.sync` for
last-resort cleanup in these rare circumstances.
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