Fix linking with LLVM_LINK_LLVM_DYLIB=ON

Linking with LLVM shared libraries currently produces linker errors.  This works around the issue
(pr24953) by disabling linking with llvm so for lldb libraries.

Patch by Evangelos Foutras.

Reviewers: zturner

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D16293

llvm-svn: 258921