[CMake] Add accurate dependency specifications

Summary:
This patch adds accurate dependency specifications to the mail LLDB libraries and tools.

In all cases except lldb-server, these dependencies are added in addition to existing dependencies (making this low risk), and I performed some code cleanup along the way.

For lldb-server I've cleaned up the LLVM dependencies down to just the minimum actually required. This is more than lldb-server actually directly references, and I've left a todo in the code to clean that up.

Reviewers: labath, zturner

Subscribers: lldb-commits, danalbert, srhines, ki.stfu, mgorny, jgosnell

Differential Revision: https://reviews.llvm.org/D29333

llvm-svn: 293686