https://blog.csdn.net/sinat_34986308/article/details/116116780?spm=1001.2101.3001.6650.1&utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7ERate-1.pc_relevant_default&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7ERate-1.pc_relevant_default&utm_relevant_index=2

deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial main
deb-src http://apt.llvm.org/xenial/ llvm-toolchain-xenial main
# 11
deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial-11 main
deb-src http://apt.llvm.org/xenial/ llvm-toolchain-xenial-11 main
# 12
deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial-12 main
deb-src http://apt.llvm.org/xenial/ llvm-toolchain-xenial-12 main