install LLVM toochain on Ubuntu18.04

install gpg key:

wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key|sudo apt-key add -

add source to /etc/apt/sources.list

# LLVM
deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic main
#deb-src http://apt.llvm.org/bionic/ llvm-toolchain-bionic main
# Needs 'sudo add-apt-repository ppa:ubuntu-toolchain-r/test' for libstdc++ with C++20 support
# 12
deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-12 main
#deb-src http://apt.llvm.org/bionic/ llvm-toolchain-bionic-12 main
# 13
deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-13 main
#deb-src http://apt.llvm.org/bionic/ llvm-toolchain-bionic-13 main

install packages(old stable):

# LLVM
sudo -E apt install libllvm-12-ocaml-dev libllvm12 llvm-12 llvm-12-dev llvm-12-doc llvm-12-examples llvm-12-runtime
# Clang and co
sudo -E apt install clang-12 clang-tools-12 clang-12-doc libclang-common-12-dev libclang-12-dev libclang1-12 clang-format-12 python3-clang-12 clangd-12 clang-tidy-12
# libfuzzer
sudo -E apt install libfuzzer-12-dev
# lldb
sudo -E apt install lldb-12
# lld (linker)
sudo -E apt install lld-12
# libc++
sudo -E apt install libc++-12-dev libc++abi-12-dev
# OpenMP
sudo -E apt install libomp-12-dev
# libclc
sudo -E apt install libclc-12-dev
# libunwind
sudo -E apt install libunwind-12-dev