Add FREEBSD-Xlist files for llvm, clang and lldb.

These are generated, and not "optimized" in any way, since I am not
entirely sure of the syntax or format of this type of file. Feel free
to suggest ways of shortening these lists.

The general idea is the same for all three files, though:

• Get rid of upstream build infrastructure (CMakeLists, Makefiles, etc)
• Delete tests, tools and utilities we don't want or use (including samples)
• Remove various bits of upstream metadata files that we don't want or use (.arcconfig, .gitignore, etc)