[test] cmake: Ensure liblldb builds before tests run
[test] cmake: Ensure liblldb builds before tests run

Without liblldb as a test dependency, tests which link it in from an
lldb framework (via Base.buildDriver()) won't work.

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@327595 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 9877e55c94e030f36f1a13bcc93bc43f1382d84a)

apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb