Doobie v0.13.4

Changed (Linux)

• Never use /tmp for JUCE's WebKit subprocess helper. Previous
  release probed /tmp and relocated $TMPDIR only if exec was
  denied. Cleaner approach: always point $TMPDIR at a user-owned
  location from the start. We prefer $XDG_RUNTIME_DIR/doobie
  (= /run/user/$UID/doobie under systemd — always exec-allowed,
  cleared at logout), falling back to ~/.cache/doobie for non-
  systemd systems. A user-set $TMPDIR is still respected. Drops
  the probe-and-warn branch in favour of always-correct.