[Cmake] Add missing dependency for running tests.

This is needed now that we marked lldb-test as EXCLUDE_ALL, to
make sure `ninja lldb-test-deps` doesn't fail.

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@358625 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed