Index: lldb/cmake/modules/LLDBConfig.cmake
===================================================================
--- lldb/cmake/modules/LLDBConfig.cmake
+++ lldb/cmake/modules/LLDBConfig.cmake
@@ -25,6 +25,12 @@
 endif()
 
 macro(add_optional_dependency variable description package found)
+  cmake_parse_arguments(ARG
+    ""
+    "VERSION"
+    ""
+    ${ARGN})
+
   set(${variable} "Auto" CACHE STRING "${description} On, Off or Auto (default)")
   string(TOUPPER "${${variable}}" ${variable})
 
@@ -40,7 +46,7 @@
   endif()
 
   if(${find_package})
-    find_package(${package} ${maybe_required})
+    find_package(${package} ${ARG_VERSION} ${maybe_required})
     set(${variable} "${${found}}")
   endif()
 
@@ -52,6 +58,7 @@
 add_optional_dependency(LLDB_ENABLE_LZMA "Enable LZMA compression support in LLDB" LibLZMA LIBLZMA_FOUND)
 add_optional_dependency(LLDB_ENABLE_LUA "Enable Lua scripting support in LLDB" Lua LUA_FOUND)
 add_optional_dependency(LLDB_ENABLE_PYTHON "Enable Python scripting support in LLDB" PythonInterpAndLibs PYTHONINTERPANDLIBS_FOUND)
+add_optional_dependency(LLDB_ENABLE_LIBXML2 "Enable Libxml 2 support in LLDB" LibXml2 LIBXML2_FOUND VERSION 2.8)
 
 option(LLDB_RELOCATABLE_PYTHON "Use the PYTHONHOME environment variable to locate Python." OFF)
 option(LLDB_USE_SYSTEM_SIX "Use six.py shipped with system and do not install a copy of it" OFF)
@@ -218,6 +225,11 @@
   include_directories(${LIBLZMA_INCLUDE_DIRS})
 endif()
 
+if (LLDB_ENABLE_LIBXML2)
+  list(APPEND system_libs ${LIBXML2_LIBRARIES})
+  include_directories(${LIBXML2_INCLUDE_DIR})
+endif()
+
 include_directories(BEFORE
   ${CMAKE_CURRENT_BINARY_DIR}/include
   ${CMAKE_CURRENT_SOURCE_DIR}/include
@@ -251,11 +263,7 @@
   endif()
 endif()
 
-if (NOT LIBXML2_FOUND)
-  find_package(LibXml2)
-endif()
-
-# Find libraries or frameworks that may be needed
+# Find Apple-specific libraries or frameworks that may be needed.
 if (APPLE)
   if(NOT IOS)
     find_library(CARBON_LIBRARY Carbon)
@@ -264,18 +272,13 @@
   find_library(FOUNDATION_LIBRARY Foundation)
   find_library(CORE_FOUNDATION_LIBRARY CoreFoundation)
   find_library(SECURITY_LIBRARY Security)
-  set(LLDB_ENABLE_LIBXML2 ON)
-  list(APPEND system_libs xml2
+  list(APPEND system_libs
        ${FOUNDATION_LIBRARY}
        ${CORE_FOUNDATION_LIBRARY}
        ${CORE_SERVICES_LIBRARY}
        ${SECURITY_LIBRARY}
        ${DEBUG_SYMBOLS_LIBRARY})
   include_directories(${LIBXML2_INCLUDE_DIR})
-elseif(LIBXML2_FOUND AND LIBXML2_VERSION_STRING VERSION_GREATER 2.8)
-  set(LLDB_ENABLE_LIBXML2 ON)
-  list(APPEND system_libs ${LIBXML2_LIBRARIES})
-  include_directories(${LIBXML2_INCLUDE_DIR})
 endif()
 
 if( WIN32 AND NOT CYGWIN )