Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -86,6 +86,11 @@
   option(LLVM_INSTALL_TOOLCHAIN_ONLY
     "Only include toolchain files in the 'install' target." OFF)
 
+  # Ensure that LLVM_ENABLE_LIBXML2 is set for standalone builds
+  if(NOT DEFINED LLVM_ENABLE_LIBXML2)
+    set(LLVM_ENABLE_LIBXML2 "ON" CACHE STRING "Use libxml2 if available. Can be ON, OFF, or FORCE_ON")
+  endif()
+
   option(LLVM_FORCE_USE_OLD_HOST_TOOLCHAIN
     "Set to ON to force using an old, unsupported host toolchain." OFF)
   option(CLANG_ENABLE_BOOTSTRAP "Generate the clang bootstrap target" OFF)
@@ -186,7 +191,7 @@
 
 # Don't look for libxml if we're using MSan, since uninstrumented third party
 # code may call MSan interceptors like strlen, leading to false positives.
-if(NOT LLVM_USE_SANITIZER MATCHES "Memory.*")
+if((LLVM_ENABLE_LIBXML2) AND (NOT LLVM_USE_SANITIZER MATCHES "Memory.*"))
   set (LIBXML2_FOUND 0)
   find_package(LibXml2 2.5.3 QUIET)
   if (LIBXML2_FOUND)
@@ -194,6 +199,10 @@
   endif()
 endif()
 
+if (LLVM_ENABLE_LIBXML2 STREQUAL "FORCE_ON" AND NOT CLANG_HAVE_LIBXML)
+  message(FATAL_ERROR "Failed to configure libxml2")
+endif()
+
 include(CheckIncludeFile)
 check_include_file(sys/resource.h CLANG_HAVE_RLIMITS)