[CMake] Deliberately get all LLVM library dependencies for standalone builds.

CMake won't expand the dependency graph for us if the dependencies are in
another project, which leads to link errors in the standalone build.
This is a refinement of r200765.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200812 91177308-0d34-0410-b5e6-96231b3b80d8