Index: libcxx/trunk/include/CMakeLists.txt
===================================================================
--- libcxx/trunk/include/CMakeLists.txt
+++ libcxx/trunk/include/CMakeLists.txt
@@ -10,11 +10,13 @@
   ${LIBCXX_SUPPORT_HEADER_PATTERN}
   )
 
-file(COPY .
-  DESTINATION "${CMAKE_BINARY_DIR}/include/c++/v1"
-  FILES_MATCHING
-  ${LIBCXX_HEADER_PATTERN}
-  )
+if(LLVM_BINARY_DIR)
+  file(COPY .
+    DESTINATION "${LLVM_BINARY_DIR}/include/c++/v1"
+    FILES_MATCHING
+    ${LIBCXX_HEADER_PATTERN}
+    )
+endif()
 
 if (LIBCXX_INSTALL_HEADERS)
   install(DIRECTORY .