[LLDB] Fixes for standalone build

[Eugene.Zelenko]

Summary

This patch include two fixes:

• include CheckAtomic to set HAVE_CXX_ATOMICS64_WITHOUT_LIB properly (introduced in r274121)
• hint Clang CMake files for LLVM CMake files location (inctroduced in ~ r274176)

[labath]

lgtm.

cmake/modules/LLDBStandalone.cmake

61

Please put a more descriptive location here, as this is the same as LLVM_BINARY_DIR. Perhaps "Path to LLVMConfig.cmake" if you can't think of anything better.

[nitesh.jain]

LGTM. Thanks

[Eugene.Zelenko]

Improved description, but in generic terms, since two files are needed.

cmake/modules/LLDBStandalone.cmake

   set(LLVM_TOOLS_BINARY_DIR ${TOOLS_BINARY_DIR} CACHE PATH "Path to llvm/bin")
   set(LLVM_LIBRARY_DIR ${LIBRARY_DIR} CACHE PATH "Path to llvm/lib")
   set(LLVM_MAIN_INCLUDE_DIR ${INCLUDE_DIR} CACHE PATH "Path to llvm/include")
+  set(LLVM_DIR ${LLVM_OBJ_ROOT}/cmake/modules/CMakeFiles CACHE PATH "Path to LLVM build tree CMake files")
   set(LLVM_BINARY_DIR ${LLVM_OBJ_ROOT} CACHE PATH "Path to LLVM build tree")
   set(LLVM_MAIN_SRC_DIR ${MAIN_SRC_DIR} CACHE PATH "Path to LLVM source tree")
 

 
   include(AddLLVM)
   include(HandleLLVMOptions)
+  include(CheckAtomic)
 
   if (PYTHON_EXECUTABLE STREQUAL "")
     set(Python_ADDITIONAL_VERSIONS 3.5 3.4 3.3 3.2 3.1 3.0 2.7 2.6 2.5)