install LLVM and clang++ 6.0+ version on Ubuntu

install_llvm_clang.sh

# ref: https://apt.llvm.org/
# 8
deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial-8 main
deb-src http://apt.llvm.org/xenial/ llvm-toolchain-xenial-8 main
wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key|sudo apt-key add -

# LLVM
apt-get install libllvm-8-ocaml-dev libllvm8 llvm-8 llvm-8-dev llvm-8-doc llvm-8-examples llvm-8-runtime
# Clang and co
apt-get install clang-8 clang-tools-8 clang-8-doc libclang-common-8-dev libclang-8-dev libclang1-8 clang-format-8 python-clang-8
# libfuzzer
apt-get install libfuzzer-8-dev
# lldb
apt-get install lldb-8
# lld (linker)
apt-get install lld-8
# libc++
apt-get install libc++-8-dev libc++abi-8-dev
# OpenMP
apt-get install libomp-8-dev