directory layout:

Makefile              the top makefile
config/targets/       contains main target specs for different instllations
config/parts/         contains part-specific variable definitions for all parts
parts/                makefiles for all parts
etc/parts.sums        the SHA256 checksums
etc/parts.master      (version part) master list
download/             [created by make] place for curl to put part tarballs in
build/                [created by make] build directory
logs/                 [created by make] build log directory for timestamps
