Clang 8 update-alternatives script

Inserts update-alternative entries for all the binaries related clang-8 and llvm and makes clang default c and c++ compiler.

Installing Clang 8

• Add the sources (for ubuntu):
  deb http://apt.llvm.org/trusty/ llvm-toolchain-trusty-8 main
deb-src http://apt.llvm.org/trusty/ llvm-toolchain-trusty-8 main
  To retrieve the archive signature:
  #: wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key|sudo apt-key add -
• Install all key packages:
  -- LLVM
  #: apt-get install libllvm-8-ocaml-dev libllvm8 llvm-8 llvm-8-dev llvm-8-doc llvm-8-examples llvm-8-runtime
  -- Clang and co
  #: apt-get install clang-8 clang-tools-8 clang-8-doc libclang-common-8-dev libclang-8-dev libclang1-8 clang-format-8 python-clang-8
  -- libfuzzer
  #: apt-get install libfuzzer-8-dev
  -- lldb
  #: apt-get install lldb-8
  -- lld (linker)
  #: apt-get install lld-8
  -- libc++
  #: apt-get install libc++-8-dev libc++abi-8-dev

Using the script

#: sudo chmod +x clang-update-alternatives.sh
#: ./clang-update-alternatives.sh