Stop building liblldb with CMake's framework functionality

Summary:
CMake has a bug in its ninja generator that prevents you from
installing targets that are built with framework support. Therefore, I want to
not rely on CMake's framework support.
See https://gitlab.kitware.com/cmake/cmake/issues/18216

Differential Revision: https://reviews.llvm.org/D49888

llvm-svn: 338154