Index: compiler-rt/CMakeLists.txt
===================================================================
--- compiler-rt/CMakeLists.txt
+++ compiler-rt/CMakeLists.txt
@@ -33,40 +33,6 @@
 include(CompilerRTUtils)
 include(CMakeDependentOption)
 
-option(COMPILER_RT_BUILD_BUILTINS "Build builtins" ON)
-mark_as_advanced(COMPILER_RT_BUILD_BUILTINS)
-option(COMPILER_RT_BUILD_CRT "Build crtbegin.o/crtend.o" ON)
-mark_as_advanced(COMPILER_RT_BUILD_CRT)
-option(COMPILER_RT_CRT_USE_EH_FRAME_REGISTRY "Use eh_frame in crtbegin.o/crtend.o" ON)
-mark_as_advanced(COMPILER_RT_CRT_USE_EH_FRAME_REGISTRY)
-option(COMPILER_RT_BUILD_SANITIZERS "Build sanitizers" ON)
-mark_as_advanced(COMPILER_RT_BUILD_SANITIZERS)
-option(COMPILER_RT_BUILD_XRAY "Build xray" ON)
-mark_as_advanced(COMPILER_RT_BUILD_XRAY)
-option(COMPILER_RT_BUILD_LIBFUZZER "Build libFuzzer" ON)
-mark_as_advanced(COMPILER_RT_BUILD_LIBFUZZER)
-option(COMPILER_RT_BUILD_PROFILE "Build profile runtime" ON)
-mark_as_advanced(COMPILER_RT_BUILD_PROFILE)
-option(COMPILER_RT_BUILD_MEMPROF "Build memory profiling runtime" ON)
-mark_as_advanced(COMPILER_RT_BUILD_MEMPROF)
-option(COMPILER_RT_BUILD_XRAY_NO_PREINIT "Build xray with no preinit patching" OFF)
-mark_as_advanced(COMPILER_RT_BUILD_XRAY_NO_PREINIT)
-option(COMPILER_RT_BUILD_ORC "Build ORC runtime" ON)
-mark_as_advanced(COMPILER_RT_BUILD_ORC)
-option(COMPILER_RT_BUILD_GWP_ASAN "Build GWP-ASan, and link it into SCUDO" ON)
-mark_as_advanced(COMPILER_RT_BUILD_GWP_ASAN)
-option(COMPILER_RT_ENABLE_CET "Build Compiler RT with CET enabled" OFF)
-
-if(FUCHSIA)
-  set(COMPILER_RT_HWASAN_WITH_INTERCEPTORS_DEFAULT OFF)
-else()
-  set(COMPILER_RT_HWASAN_WITH_INTERCEPTORS_DEFAULT ON)
-endif()
-set(COMPILER_RT_HWASAN_WITH_INTERCEPTORS ${COMPILER_RT_HWASAN_WITH_INTERCEPTORS_DEFAULT} CACHE BOOL "Enable libc interceptors in HWASan (testing mode)")
-
-set(COMPILER_RT_BAREMETAL_BUILD OFF CACHE BOOL
-  "Build for a bare-metal target.")
-
 if (COMPILER_RT_STANDALONE_BUILD)
   load_llvm_config()
   if (TARGET intrinsics_gen)
@@ -118,6 +84,61 @@
 endif()
 pythonize_bool(ANDROID)
 
+option(COMPILER_RT_BUILD_BUILTINS "Build builtins" ON)
+mark_as_advanced(COMPILER_RT_BUILD_BUILTINS)
+option(COMPILER_RT_BUILD_CRT "Build crtbegin.o/crtend.o" ON)
+mark_as_advanced(COMPILER_RT_BUILD_CRT)
+option(COMPILER_RT_CRT_USE_EH_FRAME_REGISTRY "Use eh_frame in crtbegin.o/crtend.o" ON)
+mark_as_advanced(COMPILER_RT_CRT_USE_EH_FRAME_REGISTRY)
+
+option(COMPILER_RT_BOOTSTRAP "Build just builtins and crt" OFF)
+mark_as_advanced(COMPILER_RT_BOOTSTRAP)
+
+if(COMPILER_RT_BOOTSTRAP)
+  include(AddCompilerRT)
+
+  set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
+
+  if(COMPILER_RT_BUILD_BUILTINS)
+    set(COMPILER_RT_BUILTINS_STANDALONE_BUILD TRUE)
+    add_subdirectory(lib/builtins)
+  endif()
+  if(COMPILER_RT_BUILD_CRT)
+    set(COMPILER_RT_CRT_STANDALONE_BUILD TRUE)
+    add_subdirectory(lib/crt)
+  endif()
+
+  return()
+endif()
+
+option(COMPILER_RT_BUILD_SANITIZERS "Build sanitizers" ON)
+mark_as_advanced(COMPILER_RT_BUILD_SANITIZERS)
+option(COMPILER_RT_BUILD_XRAY "Build xray" ON)
+mark_as_advanced(COMPILER_RT_BUILD_XRAY)
+option(COMPILER_RT_BUILD_LIBFUZZER "Build libFuzzer" ON)
+mark_as_advanced(COMPILER_RT_BUILD_LIBFUZZER)
+option(COMPILER_RT_BUILD_PROFILE "Build profile runtime" ON)
+mark_as_advanced(COMPILER_RT_BUILD_PROFILE)
+option(COMPILER_RT_BUILD_MEMPROF "Build memory profiling runtime" ON)
+mark_as_advanced(COMPILER_RT_BUILD_MEMPROF)
+option(COMPILER_RT_BUILD_XRAY_NO_PREINIT "Build xray with no preinit patching" OFF)
+mark_as_advanced(COMPILER_RT_BUILD_XRAY_NO_PREINIT)
+option(COMPILER_RT_BUILD_ORC "Build ORC runtime" ON)
+mark_as_advanced(COMPILER_RT_BUILD_ORC)
+option(COMPILER_RT_BUILD_GWP_ASAN "Build GWP-ASan, and link it into SCUDO" ON)
+mark_as_advanced(COMPILER_RT_BUILD_GWP_ASAN)
+option(COMPILER_RT_ENABLE_CET "Build Compiler RT with CET enabled" OFF)
+
+if(FUCHSIA)
+  set(COMPILER_RT_HWASAN_WITH_INTERCEPTORS_DEFAULT OFF)
+else()
+  set(COMPILER_RT_HWASAN_WITH_INTERCEPTORS_DEFAULT ON)
+endif()
+set(COMPILER_RT_HWASAN_WITH_INTERCEPTORS ${COMPILER_RT_HWASAN_WITH_INTERCEPTORS_DEFAULT} CACHE BOOL "Enable libc interceptors in HWASan (testing mode)")
+
+set(COMPILER_RT_BAREMETAL_BUILD OFF CACHE BOOL
+  "Build for a bare-metal target.")
+
 set(COMPILER_RT_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
 set(COMPILER_RT_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR})
 
Index: llvm/runtimes/CMakeLists.txt
===================================================================
--- llvm/runtimes/CMakeLists.txt
+++ llvm/runtimes/CMakeLists.txt
@@ -80,14 +80,16 @@
   endif()
 
   llvm_ExternalProject_Add(builtins
-                           ${compiler_rt_path}/lib/builtins
+                           ${compiler_rt_path}
                            DEPENDS ${ARG_DEPENDS}
                            CMAKE_ARGS -DLLVM_LIBRARY_OUTPUT_INTDIR=${LLVM_LIBRARY_DIR}
                                       -DLLVM_RUNTIME_OUTPUT_INTDIR=${LLVM_TOOLS_BINARY_DIR}
                                       -DLLVM_DEFAULT_TARGET_TRIPLE=${LLVM_TARGET_TRIPLE}
                                       -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=${LLVM_ENABLE_PER_TARGET_RUNTIME_DIR_default}
                                       -DCMAKE_C_COMPILER_WORKS=ON
+                                      -DCMAKE_CXX_COMPILER_WORKS=ON
                                       -DCMAKE_ASM_COMPILER_WORKS=ON
+                                      -DCOMPILER_RT_BOOTSTRAP=ON
                                       ${COMMON_CMAKE_ARGS}
                                       ${BUILTINS_CMAKE_ARGS}
                            PASSTHROUGH_PREFIXES COMPILER_RT
@@ -114,15 +116,17 @@
   endforeach()
 
   llvm_ExternalProject_Add(builtins-${target}
-                           ${compiler_rt_path}/lib/builtins
+                           ${compiler_rt_path}
                            DEPENDS ${ARG_DEPENDS}
                            CMAKE_ARGS -DLLVM_LIBRARY_OUTPUT_INTDIR=${LLVM_LIBRARY_DIR}
                                       -DLLVM_RUNTIME_OUTPUT_INTDIR=${LLVM_TOOLS_BINARY_DIR}
                                       -DLLVM_DEFAULT_TARGET_TRIPLE=${target}
                                       -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON
                                       -DCMAKE_C_COMPILER_WORKS=ON
+                                      -DCMAKE_CXX_COMPILER_WORKS=ON
                                       -DCMAKE_ASM_COMPILER_WORKS=ON
                                       -DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON
+                                      -DCOMPILER_RT_BOOTSTRAP=ON
                                       ${COMMON_CMAKE_ARGS}
                                       ${${target}_extra_args}
                            USE_TOOLCHAIN
@@ -239,7 +243,8 @@
                            ${CMAKE_CURRENT_SOURCE_DIR}/../../runtimes
                            DEPENDS ${ARG_DEPENDS}
                            # Builtins were built separately above
-                           CMAKE_ARGS -DCOMPILER_RT_BUILD_BUILTINS=Off
+                           CMAKE_ARGS -DCOMPILER_RT_BUILD_BUILTINS=OFF
+                                      -DCOMPILER_RT_BUILD_CRT=OFF
                                       -DLLVM_INCLUDE_TESTS=${LLVM_INCLUDE_TESTS}
                                       -DLLVM_DEFAULT_TARGET_TRIPLE=${LLVM_TARGET_TRIPLE}
                                       -DLLVM_ENABLE_PROJECTS_USED=${LLVM_ENABLE_PROJECTS_USED}
@@ -354,7 +359,8 @@
                            ${CMAKE_CURRENT_SOURCE_DIR}/../../runtimes
                            DEPENDS ${${name}_deps}
                            # Builtins were built separately above
-                           CMAKE_ARGS -DCOMPILER_RT_BUILD_BUILTINS=Off
+                           CMAKE_ARGS -DCOMPILER_RT_BUILD_BUILTINS=OFF
+                                      -DCOMPILER_RT_BUILD_CRT=OFF
                                       -DLLVM_INCLUDE_TESTS=${LLVM_INCLUDE_TESTS}
                                       -DLLVM_DEFAULT_TARGET_TRIPLE=${target}
                                       -DLLVM_ENABLE_PROJECTS_USED=${LLVM_ENABLE_PROJECTS_USED}