I have been trying and here my conclusions:

• The faust2esp gives you a full component for esp, that is half broken, so dont use it.
• Focus using the example from faust, this one. Still I am having problems because of things being deprecated. You need to use idf-v3

It is necessary to modify the main/CMakeLists.txt as:

set(COMPONENT_SRCS "main.cpp" "FaustSawtooth.cpp" "WM8978.cpp")
set(COMPONENT_ADD_INCLUDEDIRS ".")

register_component()

And it is possible to compile.

Build project

$ export IDF_PATH=~/esp/esp-idf-v3
$ . ./export.sh