[CMake] Add the system debugserver to lldb-test-deps.
[CMake] Add the system debugserver to lldb-test-deps.

When using the system debugserver we create a target to copy it over.
This target has to be added to lldb-test-deps.

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@372901 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 6afe53e82e0eaccc4bd61b1b62d0b121a03243f5)

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