This way bash won't expand and post-process variable values in any way.
The changes are driven with
[`shellcheck`](https://github.com/koalaman/shellcheck)
Notable changes:
- javaScriptEnabled moved to the browser side.
- enabling new UI since it no longer helps to fix screencast
Review branch: https://github.com/aslushnikov/juggler/tree/roll-to-91-0-b10
Note: this will have 2 screencast tests failing. Investigation is in a follow-up.
Browsers require particular xcode versions to be installed on the host
machine to produce successful build.
This patch starts using explicit xcode versions for all mac browser
builds.
