Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -720,6 +720,8 @@
   add_subdirectory(tools)
 endif()
 
+add_subdirectory(runtimes)
+
 if( LLVM_INCLUDE_EXAMPLES )
   add_subdirectory(examples)
 endif()
@@ -730,7 +732,8 @@
     llvm_ExternalProject_Add(test-suite ${LLVM_MAIN_SRC_DIR}/projects/test-suite
       USE_TOOLCHAIN
       EXCLUDE_FROM_ALL
-      NO_INSTALL)
+      NO_INSTALL
+      ALWAYS_CLEAN)
   endif()
   add_subdirectory(test)
   add_subdirectory(unittests)
Index: cmake/modules/LLVMExternalProjectUtils.cmake
===================================================================
--- cmake/modules/LLVMExternalProjectUtils.cmake
+++ cmake/modules/LLVMExternalProjectUtils.cmake
@@ -29,7 +29,8 @@
 #     Extra targets in the subproject to generate targets for
 #   )
 function(llvm_ExternalProject_Add name source_dir)
-  cmake_parse_arguments(ARG "USE_TOOLCHAIN;EXCLUDE_FROM_ALL;NO_INSTALL"
+  cmake_parse_arguments(ARG
+    "USE_TOOLCHAIN;EXCLUDE_FROM_ALL;NO_INSTALL;ALWAYS_CLEAN"
     "SOURCE_DIR"
     "CMAKE_ARGS;TOOLCHAIN_TOOLS;RUNTIME_LIBRARIES;DEPENDS;EXTRA_TARGETS" ${ARGN})
   canonicalize_tool_name(${name} nameCanon)
@@ -52,6 +53,10 @@
     endif()
   endforeach()
 
+  if(ARG_ALWAYS_CLEAN)
+    set(always_clean clean)
+  endif()
+
   list(FIND TOOLCHAIN_TOOLS clang FOUND_CLANG)
   if(FOUND_CLANG GREATER -1)
     set(CLANG_IN_TOOLCHAIN On)
@@ -135,6 +140,14 @@
     CMAKE_ARGS ${${nameCanon}_CMAKE_ARGS}
                ${compiler_args}
                -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX}
+               -DLLVM_CONFIG_PATH=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-config
+               -DLLVM_LIBRARY_OUTPUT_INTDIR=${LLVM_LIBRARY_OUTPUT_INTDIR}
+               -DLLVM_RUNTIME_OUTPUT_INTDIR=${LLVM_RUNTIME_OUTPUT_INTDIR}
+               -DLLVM_LIBDIR_SUFFIX=${LLVM_LIBDIR_SUFFIX}
+               -DLLVM_ENABLE_WERROR=${LLVM_ENABLE_WERROR}
+               -DPACKAGE_VERSION=${PACKAGE_VERSION}
+               -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
+               -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
                ${ARG_CMAKE_ARGS}
                ${PASSTHROUGH_VARIABLES}
     INSTALL_COMMAND ""
@@ -152,7 +165,7 @@
     ExternalProject_Add_Step(${name} force-rebuild
       COMMAND ${run_build}
       COMMENT "Forcing rebuild of ${name}"
-      DEPENDEES configure clean
+      DEPENDEES configure ${always_clean}
       DEPENDS ${ALWAYS_REBUILD} ${ARG_DEPENDS} ${TOOLCHAIN_BINS}
       ${cmake_3_4_USES_TERMINAL} )
   endif()
Index: runtimes/CMakeLists.txt
===================================================================
--- /dev/null
+++ runtimes/CMakeLists.txt
@@ -0,0 +1,16 @@
+include(LLVMExternalProjectUtils)
+
+# Discover the projects that use CMake in the subdirectories.
+# Note that explicit cmake invocation is required every time a new project is
+# added or removed.
+
+add_custom_target(runtimes)
+
+file(GLOB entries *)
+foreach(entry ${entries})
+  if(IS_DIRECTORY ${entry} AND EXISTS ${entry}/CMakeLists.txt)
+    get_filename_component(projName ${entry} NAME)
+    llvm_ExternalProject_Add(${projName} ${entry} USE_TOOLCHAIN)
+    add_dependencies(runtimes ${projName})
+  endif()
+endforeach(entry)