Dumper tests: Use lldb from /Applications/Xcode by default on Mac

Change-Id: I1974a6ad63a914d860fa99e55cf0162774ab7b07
Reviewed-by: hjk <hjk121@nokiamail.com>
Revert "Welcome: Store examples search text in settings"

This reverts commit 894ade6f1e2767a8866642a4ea278659730c26d8

Storing the search text was not thought well through. It causes bad user experience.

Also, the real solution for showing filtered Example sets in the chooser is coming here: https://codereview.qt-project.org/#change,82906

Change-Id: Ibb51bf5c0fa08fdeb8530a19d823ba97a3c167d1
Reviewed-by: Eike Ziller <eike.ziller@digia.com>