Add clang.

toolset/setup/linux/prerequisites.sh

@@ -62,10 +62,10 @@ sudo pip install colorama==0.3.1
 sudo pip install progressbar==2.2
 sudo pip install requests
 
-# Install gcc-4.8 and gcc-4.9
+# Install gcc-4.8, gcc-4.9 and clang
 sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
 sudo apt-get -yq update
-sudo apt-get install -qqy gcc-4.8 g++-4.8 gcc-4.9 g++-4.9
+sudo apt-get install -qqy gcc-4.8 g++-4.8 gcc-4.9 g++-4.9 clang
 
 # Stop permanently overwriting people's files just for 
 # trying out our software!