Import prebuilt clang toolchain for linux.
diff --git a/linux-x64/clang/lib64/cmake/llvm/LLVMInstallSymlink.cmake b/linux-x64/clang/lib64/cmake/llvm/LLVMInstallSymlink.cmake
new file mode 100644
index 0000000..1a04de9
--- /dev/null
+++ b/linux-x64/clang/lib64/cmake/llvm/LLVMInstallSymlink.cmake
@@ -0,0 +1,21 @@
+# We need to execute this script at installation time because the
+# DESTDIR environment variable may be unset at configuration time.
+# See PR8397.
+
+function(install_symlink name target outdir)
+  if(CMAKE_HOST_UNIX)
+    set(LINK_OR_COPY create_symlink)
+    set(DESTDIR $ENV{DESTDIR})
+  else()
+    set(LINK_OR_COPY copy)
+  endif()
+
+  set(bindir "${DESTDIR}${CMAKE_INSTALL_PREFIX}/${outdir}/")
+
+  message("Creating ${name}")
+
+  execute_process(
+    COMMAND "${CMAKE_COMMAND}" -E ${LINK_OR_COPY} "${target}" "${name}"
+    WORKING_DIRECTORY "${bindir}")
+
+endfunction()