Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -428,15 +428,17 @@
 
 add_subdirectory(include)
 
-foreach(path IN ITEMS ${LLVM_MAIN_SRC_DIR}/projects/libcxx
-                      ${LLVM_MAIN_SRC_DIR}/runtimes/libcxx
-                      ${LLVM_MAIN_SRC_DIR}/../libcxx
-                      ${LLVM_EXTERNAL_LIBCXX_SOURCE_DIR})
-  if(IS_DIRECTORY ${path})
-    set(COMPILER_RT_LIBCXX_PATH ${path})
-    break()
-  endif()
-endforeach()
+if(LLVM_TOOL_LIBCXX_BUILD)
+  foreach(path IN ITEMS ${LLVM_MAIN_SRC_DIR}/projects/libcxx
+                        ${LLVM_MAIN_SRC_DIR}/runtimes/libcxx
+                        ${LLVM_MAIN_SRC_DIR}/../libcxx
+                        ${LLVM_EXTERNAL_LIBCXX_SOURCE_DIR})
+    if(IS_DIRECTORY ${path})
+      set(COMPILER_RT_LIBCXX_PATH ${path})
+      break()
+    endif()
+  endforeach()
+endif()
 
 set(COMPILER_RT_LLD_PATH ${LLVM_MAIN_SRC_DIR}/tools/lld)
 if(EXISTS ${COMPILER_RT_LLD_PATH}/ AND LLVM_TOOL_LLD_BUILD)