Compute folders of "includes" / using -dump-prefs


I’m trying to “dump” the actual folders of includes, and preprocessor definitions, before compiling.
For that purpose I found the -dump-prefs option of the command line tool arduino-builder.

However, the result still contains some place holders, which I cannot find how to resolve.

E.g, for “-fqbn=arduino:avr:mega:cpu=atmega2560” on my machine,
This the value for recipe.preproc.includes is

recipe.preproc.includes="{compiler.path}{compiler.cpp.cmd}" {compiler.cpp.flags} {preproc.includes.flags} -mmcu={build.mcu} -DF_CPU={build.f_cpu} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {compiler.cpp.extra_flags} {build.extra_flags} {includes} “{source_file}”

I mange to find the values for place holders in the same dump,
except for {includes}

Any idea where I can find it, or how is it done ?
Other way ?
Thanks for your help.