`attemptBoot` only listened on `child.on('exit', ...)`, so a `spawn` failure
(ENOENT — emulator binary missing/EACCES, transient FS hiccup) emitted an
`error` event with no listener and Node crashed the tool-server with an
uncaught exception while leaking the in-flight Map entry. Funnel the error
into the same `earlyExitError` race so the boot promise rejects cleanly and
`bootAndroid`'s `finally` clears the map.
Ignacy Łątka
5ea8a9936a