diff --git a/clang/CMakeLists.txt b/clang/CMakeLists.txt
--- a/clang/CMakeLists.txt
+++ b/clang/CMakeLists.txt
@@ -706,6 +706,7 @@
     CMAKE_CXX_COMPILER_LAUNCHER
     CMAKE_MAKE_PROGRAM
     CMAKE_OSX_ARCHITECTURES
+    CMAKE_BUILD_TYPE
     LLVM_ENABLE_PROJECTS
     LLVM_ENABLE_RUNTIMES)