$ sudo apt-get update
$ sudo apt-get install clang-3.8 

clang-3.8 is installed in your system.

Make ensure the clang-3.8 package were installed using the commands given below,

$ sudo dpkg-query -l | grep clang-3.8 *

You will get with clang-3.8 package name, version, architecture and description in a table

clang-3.8 package basic information: