Another quick bug-fix release, fixing an issue where frida-helper on Darwin and Linux kept the embedder’s stdio pipes open.

The helper previously inherited these streams at launch so they could later be used by Device#spawn() with stdio='inherit'. The streams are now passed to the helper with each such request instead.

• darwin: Redirect the helper’s own stdin, stdout, and stderr to /dev/null.
• linux: Apply the same fix as on Darwin.