Go to https://developer.apple.com/downloads/, log in and then download http://adcdownload.apple.com/Developer_Tools/Command_Line_Tools_OS_X_10.11_for_Xcode_7.2/Command_Line_Tools_OS_X_10.11_for_Xcode_7.2.dmg, and install, as was suggested by fabregaszy.
Run the following command to switch to the old version:
sudo xcode-select --switch /Library/Developer/CommandLineTools
Run the following command to quickly check clang version:
clang --version