Connect LLVM CMake build scripts to LLDB's CMake scripts:
- if you have LLDB checked out in $llvm/tools, CMake will build it now!
- LLDB is known to build on Linux with libstdc++ and GCC 4.6/4.7 or Clang 3.3
- to run lldb tests, do "make check-lldb" after a build



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176307 91177308-0d34-0410-b5e6-96231b3b80d8