Add ability to make clang compile time plugins

[dpeter99]

If it is possible I would really love the ability to include the necessary libs for clang plugin development. Currently, all docs suggest building all of clang manually to have this ability, and no pre-built package includes them as far as I found. While on linux and macos they are available through the package manager.

This would certainly increase the package size.

https://clang.llvm.org/docs/ClangPlugins.html

I'm hoping to use this for my thesis project which includes a small reflection lib. With this, I could add new attributes for influencing how the reflection is done.