advanced build configurations

Hello Clang people,

are the build configurations described here still up to date?

I’ve tried the pgo and the 3 stage builds and in all case I don’t get the ninja (or make) targets described.

In case it makes a difference, I’m building with llvm and clang as peer directories and LLVM_EXTERNAL_PROJECTS=“clang” together with LLVM_EXTERNAL_CLANG_TOOLS_EXTRA_SOURCE_DIR.

Any hint?