Modern clang docker containers

A docker container with modern cmake and clang. The cmake version provided by silkeh/clang is too old for me, so I created this container.

Tags and corresponding docker files:

• 11: 11.Dockerfile/ contains
  • clang-11
  • clang-tidy-11
  • clang-format-11
  • cmake 3.16.3
  • gcovr 4.2
  • libc++-11-dev
  • llvm-tools-11
• 12: 12.Dockerfile/ contains
  • clang-12
  • clang-tidy-12
  • clang-format-12
  • cmake 3.16.3
  • gcovr 4.2
  • libc++-12-dev
  • llvm-tools-12
• latest links to 12.Dockerfile/.