The root CMake project (CMakeLists.txt, cmake/) builds the core, libraries and sketches outside the Arduino IDE. It gets its compiler and link flags by reading platform/platform.txt, boards.txt and platform.local.txt (cmake/arduino_properties.cmake), not from a copy.

A second hand-written flag list would drift from the Arduino build, and the CMake build would then "verify" something users never get. Reading the same files keeps one source of truth; the identical ELF size for the same sketch confirms it.

A small property expander in CMake. Recipes (recipe.*.pattern) are not executed; the CMake link step mirrors recipe.c.combine.pattern by hand, so a change to that recipe must be repeated in cmake/phyduino.cmake. Nothing CMake-related goes into platform/, and make_release.py excludes CMake files from the zip regardless.