Index: compiler-rt/cmake/Modules/CompilerRTCompile.cmake
===================================================================
--- compiler-rt/cmake/Modules/CompilerRTCompile.cmake
+++ compiler-rt/cmake/Modules/CompilerRTCompile.cmake
@@ -131,10 +131,7 @@
       "    then echo 'e.g. with:'"
       "    echo '  cp -r' $(dirname $(dirname $(xcrun -f clang)))/lib/c++ '${LLVM_BINARY_DIR}/include/'"
       "  fi"
-      "  echo 'This can also be fixed by checking out the libcxx project from llvm.org and installing the headers'"
-      "  echo 'into your build directory:'"
-      "  echo '  cd ${LLVM_MAIN_SRC_DIR}/projects && svn co http://llvm.org/svn/llvm-project/libcxx/trunk libcxx'"
-      "  echo '  cd ${LLVM_BINARY_DIR} && make -C ${LLVM_MAIN_SRC_DIR}/projects/libcxx installheaders HEADER_DIR=${LLVM_BINARY_DIR}/include'"
+      "  echo 'This can also be fixed by adding libcxx to LLVM_ENABLE_PROJECTS and building the cxx-headers target.'"
       "  echo"
       "  false"
       "fi"
Index: compiler-rt/cmake/base-config-ix.cmake
===================================================================
--- compiler-rt/cmake/base-config-ix.cmake
+++ compiler-rt/cmake/base-config-ix.cmake
@@ -101,24 +101,6 @@
 endif()
 
 if(APPLE)
-  # On Darwin if /usr/include/c++ doesn't exist, the user probably has Xcode but
-  # not the command line tools (or is using macOS 10.14 or newer). If this is
-  # the case, we need to find the OS X sysroot to pass to clang.
-  if(NOT EXISTS /usr/include/c++)
-    execute_process(COMMAND xcrun -sdk macosx --show-sdk-path
-       OUTPUT_VARIABLE OSX_SYSROOT
-       ERROR_QUIET
-       OUTPUT_STRIP_TRAILING_WHITESPACE)
-    if (NOT OSX_SYSROOT OR NOT EXISTS ${OSX_SYSROOT})
-      message(WARNING "Detected OSX_SYSROOT ${OSX_SYSROOT} does not exist")
-    else()
-      message(STATUS "Found OSX_SYSROOT: ${OSX_SYSROOT}")
-      set(OSX_SYSROOT_FLAG "-isysroot${OSX_SYSROOT}")
-    endif()
-  else()
-    set(OSX_SYSROOT_FLAG "")
-  endif()
-
   option(COMPILER_RT_ENABLE_IOS "Enable building for iOS" On)
   option(COMPILER_RT_ENABLE_WATCHOS "Enable building for watchOS - Experimental" Off)
   option(COMPILER_RT_ENABLE_TVOS "Enable building for tvOS - Experimental" Off)
Index: compiler-rt/cmake/config-ix.cmake
===================================================================
--- compiler-rt/cmake/config-ix.cmake
+++ compiler-rt/cmake/config-ix.cmake
@@ -363,6 +363,14 @@
     endif()
   endif()
 
+  # /usr/include/c++ doesn't exist on macOS 10.14 or newer.
+  # If this is the case, we need to find the OS X sysroot to pass to clang.
+  if(NOT EXISTS /usr/include/c++)
+    set(OSX_SYSROOT_FLAG "-isysroot${DARWIN_osx_SYSROOT}")
+  else()
+    set(OSX_SYSROOT_FLAG "")
+  endif()
+
   if(COMPILER_RT_ENABLE_IOS)
     list(APPEND DARWIN_EMBEDDED_PLATFORMS ios)
     set(DARWIN_ios_MIN_VER 9.0)