Index: cmake/Modules/AddCompilerRT.cmake
===================================================================
--- cmake/Modules/AddCompilerRT.cmake
+++ cmake/Modules/AddCompilerRT.cmake
@@ -469,32 +469,35 @@
     message(FATAL_ERROR "libcxx not found!")
   endif()
 
-  cmake_parse_arguments(LIBCXX "" "" "DEPS;CFLAGS;CMAKE_ARGS" ${ARGN})
+  cmake_parse_arguments(LIBCXX "USE_TOOLCHAIN;NO_INSTALL" "" "DEPS;CFLAGS;CMAKE_ARGS" ${ARGN})
   foreach(flag ${LIBCXX_CFLAGS})
     set(flagstr "${flagstr} ${flag}")
   endforeach()
   set(LIBCXX_CFLAGS ${flagstr})
 
-  if(NOT COMPILER_RT_STANDALONE_BUILD)
-    list(APPEND LIBCXX_DEPS clang)
+  if(LIBCXX_USE_TOOLCHAIN)
+    set(compiler_args -DCMAKE_C_COMPILER=${COMPILER_RT_TEST_COMPILER}
+                      -DCMAKE_CXX_COMPILER=${COMPILER_RT_TEST_CXX_COMPILER})
+    if(NOT COMPILER_RT_STANDALONE_BUILD)
+      set(force_deps DEPENDS clang)
+    endif()
   endif()
 
   ExternalProject_Add(${name}
+		DEPENDS ${LIBCXX_DEPS}
     PREFIX ${prefix}
     SOURCE_DIR ${COMPILER_RT_LIBCXX_PATH}
     CMAKE_ARGS -DCMAKE_MAKE_PROGRAM:STRING=${CMAKE_MAKE_PROGRAM}
-               -DCMAKE_C_COMPILER=${COMPILER_RT_TEST_COMPILER}
-               -DCMAKE_CXX_COMPILER=${COMPILER_RT_TEST_CXX_COMPILER}
+               ${compiler_args}
                -DCMAKE_C_FLAGS=${LIBCXX_CFLAGS}
                -DCMAKE_CXX_FLAGS=${LIBCXX_CFLAGS}
                -DCMAKE_BUILD_TYPE=Release
-               -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
                -DLLVM_PATH=${LLVM_MAIN_SRC_DIR}
                -DLIBCXX_STANDALONE_BUILD=On
                ${LIBCXX_CMAKE_ARGS}
+    INSTALL_COMMAND ""
     LOG_BUILD 1
     LOG_CONFIGURE 1
-    LOG_INSTALL 1
     )
   set_target_properties(${name} PROPERTIES EXCLUDE_FROM_ALL TRUE)
 
@@ -508,8 +511,19 @@
     COMMAND ${CMAKE_COMMAND} -E make_directory <BINARY_DIR>
     COMMENT "Clobberring ${name} build directory..."
     DEPENDERS configure
-    DEPENDS ${LIBCXX_DEPS}
+    ${force_deps}
     )
+
+  if(NOT LIBCXX_NO_INSTALL)
+    install(CODE "execute_process\(COMMAND \${CMAKE_COMMAND} -DCMAKE_INSTALL_PREFIX=\${CMAKE_INSTALL_PREFIX} -P ${BINARY_DIR}/cmake_install.cmake \)"
+      COMPONENT ${name})
+    add_custom_target(install-${name}
+                      DEPENDS ${name}
+                      COMMAND "${CMAKE_COMMAND}"
+                              -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX}
+                              -P "${CMAKE_BINARY_DIR}/cmake_install.cmake"
+                      USES_TERMINAL)
+  endif()
 endmacro()
 
 function(rt_externalize_debuginfo name)
Index: lib/fuzzer/CMakeLists.txt
===================================================================
--- lib/fuzzer/CMakeLists.txt
+++ lib/fuzzer/CMakeLists.txt
@@ -97,11 +97,12 @@
     set(LIBCXX_${arch}_PREFIX ${CMAKE_CURRENT_BINARY_DIR}/libcxx_fuzzer_${arch})
     add_custom_libcxx(libcxx_fuzzer_${arch} ${LIBCXX_${arch}_PREFIX}
       CFLAGS ${TARGET_CFLAGS}
-             -D_LIBCPP_ABI_VERSION=__Fuzzer
+             -D_LIBCPP_ABI_VERSION=Fuzzer
              -D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS=1
              -fvisibility=hidden
       CMAKE_ARGS -DLIBCXX_ENABLE_EXCEPTIONS=OFF
-                 -DLIBCXX_CXX_ABI=none)
+                 -DLIBCXX_CXX_ABI=none
+			NO_INSTALL)
     target_compile_options(RTfuzzer.${arch} PRIVATE -isystem ${LIBCXX_${arch}_PREFIX}/include/c++/v1)
     add_dependencies(RTfuzzer.${arch} libcxx_fuzzer_${arch})
     target_compile_options(RTfuzzer_main.${arch} PRIVATE -isystem ${LIBCXX_${arch}_PREFIX}/include/c++/v1)
Index: lib/msan/tests/CMakeLists.txt
===================================================================
--- lib/msan/tests/CMakeLists.txt
+++ lib/msan/tests/CMakeLists.txt
@@ -128,7 +128,8 @@
     set(LIBCXX_PREFIX ${CMAKE_CURRENT_BINARY_DIR}/../libcxx_msan_${arch})
     add_custom_libcxx(libcxx_msan_${arch} ${LIBCXX_PREFIX}
       DEPS ${MSAN_RUNTIME_LIBRARIES}
-      CFLAGS ${MSAN_LIBCXX_CFLAGS} ${TARGET_CFLAGS})
+      CFLAGS ${MSAN_LIBCXX_CFLAGS} ${TARGET_CFLAGS}
+      USE_TOOLCHAIN)
     set(MSAN_LIBCXX_SO ${LIBCXX_PREFIX}/lib/libc++.so)
 
     add_msan_tests_for_arch(${arch} "" "")
Index: lib/tsan/CMakeLists.txt
===================================================================
--- lib/tsan/CMakeLists.txt
+++ lib/tsan/CMakeLists.txt
@@ -212,7 +212,8 @@
     set(LIBCXX_PREFIX ${CMAKE_CURRENT_BINARY_DIR}/libcxx_tsan_${arch})
     add_custom_libcxx(libcxx_tsan_${arch} ${LIBCXX_PREFIX}
       DEPS ${TSAN_RUNTIME_LIBRARIES}
-      CFLAGS ${TARGET_CFLAGS} -fsanitize=thread)
+      CFLAGS ${TARGET_CFLAGS} -fsanitize=thread
+      USE_TOOLCHAIN)
     list(APPEND libcxx_tsan_deps libcxx_tsan_${arch})
   endforeach()