When IDF_BUILD_V2 evaluates to a CMake-truthy value, project.cmake
delegates to Build system v2 (cmakev2). The shim wraps project(),
forwards the app-declared COMPONENTS list via __SHIM_COMPONENTS, and
publishes __V1_COMPAT_SHIM so Build system v2 internals can gate Build
system v1 compatibility behavior. Existing app CMakeLists.txt files
build unchanged.
Co-authored-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>