Follow: LibTooling and LibASTMatchers installation tutorial if you want to contribute.
Use gold or lld because bfd use too much ram
wget or curl --progress-bar -LO
wget https://github.com/llvm/llvm-project/archive/refs/tags/llvmorg-12.0.1.tar.gz
tar xvf llvmorg-12.0.1.tar.gz
cd llvm-project-llvmorg-12.0.1
cmake -G Ninja -S ./llvm -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra;lld" -DCMAKE_BUILD_TYPE=Release -DLLVM_USE_LINKER=gold -B build
# export CC=`which clang`
# export CXX=`which clang++`
# export CFLAGS='-fuse-ld=ld.lld -rtlib=compiler-rt'
# export CXXFLAGS='-fuse-ld=lld' # gcc
# export CXXFLAGS='-B lld' # clang
# sudo update-alternatives --install "/usr/bin/ld" "ld" `which ld.lld` 10
cmake --build build -- -j`nproc`
sudo cmake --install build
cd build
ninja install# uninstall from build
xargs rm < install_manifest.txt