Specify the dependencies of lldb-server manually

Summary:
This basically just inlines the LLDBDependencies.cmake file into lldb-server
CMakeLists.txt. The reason is that most of these dependencies are not actually
necessary for lldb-server (some of them can't be removed because of
cross-dependencies, but most of the plugins can). I intend to start cleaning
these up in follow-up commits, but I want to do this first, so the subsequent
ones can be easily reverted if they don't build in some configurations.

When I cleaned these up locally, I was able to get a 30%--50% improvement in
lldb-server size.

Reviewers: zturner, beanz, tfiala

Subscribers: danalbert, srhines, lldb-commits, mgorny

Differential Revision: https://reviews.llvm.org/D26975

llvm-svn: 288159