Revert "update clang to 40eb7b4b92dc52e6d757b133899b40395e6adfb4"

This reverts commit 7b8fb02b5aeb43c65b040bcde0a93b434a8cfff4.
add clang ref to 95eef3a6f715bd0672cba5934e477e6b8b66914c