Enforce that only the LLDB API unit tests can link liblldb

[JDevlieghere]

Enforce that only the LLDB API unit tests (lldb/unittests/API) can link liblldb. All the other unit tests statically link the private libraries, and linking liblldb there too means you end up with two copies of the same symbols, which leads to various (hard-to-debug) issues.

[llvmbot]

@llvm/issue-subscribers-lldb

Author: Jonas Devlieghere (JDevlieghere)

Enforce that only the LLDB API unit tests (`lldb/unittests/API`) can link liblldb. All the other unit tests statically link the private libraries, and linking `liblldb` there too means you end up with two copies of the same symbols, which leads to various (hard-to-debug) issues.