objective-caml: ensure symlinked directory exists.

Closes #33614.
objective-caml: update 4.02.1 bottle.

Closes #33617.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
brew-test-bot: add fail-fast option.

Allows easier testing of failures due to bad state.
formula_installer: set exit code to failed always.

If we say something failed we should communicate that through the exit
code for the bot and scripts.
node: bump npm to 2.1.5.
WIP