LLDB standalone build: check if Clang was built independently from LLVM

This is fix for bug 23704: LLDB standalone build always include
ClangConfig.cmake even if Clang was built with LLVM (ClangConfig.cmake
doesn't exist).

Patch by: Eugene Zelenko

llvm-svn: 240419

lldb/CMakeLists.txt

@@ -85,7 +85,9 @@ if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
 
   # Import CMake library targets from LLVM and Clang.
   include("${LLDB_PATH_TO_LLVM_BUILD}/share/llvm/cmake/LLVMConfig.cmake")
-  include("${LLDB_PATH_TO_CLANG_BUILD}/share/clang/cmake/ClangConfig.cmake")
+  if ( EXISTS "${LLDB_PATH_TO_CLANG_BUILD}/share/clang/cmake/ClangConfig.cmake" )
+    include("${LLDB_PATH_TO_CLANG_BUILD}/share/clang/cmake/ClangConfig.cmake")
+  endif()
 
   set(PACKAGE_VERSION "${LLVM_PACKAGE_VERSION}")