Index: compiler-rt/trunk/CMakeLists.txt
===================================================================
--- compiler-rt/trunk/CMakeLists.txt
+++ compiler-rt/trunk/CMakeLists.txt
@@ -157,17 +157,14 @@
   set(SANITIZER_CXX_ABI_SYSTEM 1)
 endif()
 
-set(COMPILER_RT_RUNTIME "default" CACHE STRING
-    "Compiler runtime to use.")
-
-if (COMPILER_RT_RUNTIME STREQUAL "default")
-  if (FUCHSIA)
-    set(COMPILER_RT_RUNTIME_LIBRARY "builtins")
-  endif()
-else()
-  set(COMPILER_RT_RUNTIME_LIBRARY "${COMPILER_RT_RUNTIME}")
+set(DEFAULT_COMPILER_RT_USE_BUILTINS_LIBRARY OFF)
+if (FUCHSIA)
+  set(DEFAULT_COMPILER_RT_USE_BUILTINS_LIBRARY ON)
 endif()
 
+option(COMPILER_RT_USE_BUILTINS_LIBRARY
+  "Use compiler-rt builtins instead of libgcc" ${DEFAULT_COMPILER_RT_USE_BUILTINS_LIBRARY})
+
 include(config-ix)
 
 #================================
@@ -316,7 +313,7 @@
 # Set common link flags.
 append_list_if(COMPILER_RT_HAS_NODEFAULTLIBS_FLAG -nodefaultlibs SANITIZER_COMMON_LINK_FLAGS)
 
-if (COMPILER_RT_RUNTIME_LIBRARY STREQUAL "builtins")
+if (COMPILER_RT_USE_BUILTINS_LIBRARY)
   list(APPEND SANITIZER_COMMON_LINK_LIBS ${COMPILER_RT_BUILTINS_LIBRARY})
 else()
   if (ANDROID)
Index: compiler-rt/trunk/cmake/config-ix.cmake
===================================================================
--- compiler-rt/trunk/cmake/config-ix.cmake
+++ compiler-rt/trunk/cmake/config-ix.cmake
@@ -13,7 +13,7 @@
 endfunction()
 
 check_library_exists(c fopen "" COMPILER_RT_HAS_LIBC)
-if (COMPILER_RT_RUNTIME_LIBRARY STREQUAL "builtins")
+if (COMPILER_RT_USE_BUILTINS_LIBRARY)
   include(HandleCompilerRT)
   find_compiler_rt_library(builtins COMPILER_RT_BUILTINS_LIBRARY)
 else()
@@ -30,7 +30,7 @@
   if (COMPILER_RT_HAS_LIBC)
     list(APPEND CMAKE_REQUIRED_LIBRARIES c)
   endif ()
-  if (COMPILER_RT_RUNTIME_LIBRARY STREQUAL "builtins")
+  if (COMPILER_RT_USE_BUILTINS_LIBRARY)
     list(APPEND CMAKE_REQUIRED_LIBRARIES "${COMPILER_RT_BUILTINS_LIBRARY}")
   elseif (COMPILER_RT_HAS_GCC_S_LIB)
     list(APPEND CMAKE_REQUIRED_LIBRARIES gcc_s)