Index: llvm/trunk/CMakeLists.txt
===================================================================
--- llvm/trunk/CMakeLists.txt
+++ llvm/trunk/CMakeLists.txt
@@ -51,7 +51,7 @@
 
 if (NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
   message(STATUS "No build type selected, default to Debug")
-  set(CMAKE_BUILD_TYPE "Debug" CACHE STRING "Build type (default Debug)")
+  set(CMAKE_BUILD_TYPE "Debug" CACHE STRING "Build type (default Debug)" FORCE)
 endif()
 
 # This should only apply if you are both on an Apple host, and targeting Apple.