T= now names a specific board (qemu, pc, pi4, pi5, milkv) rather than
an arch alias. mk/boards.mk is the single table: sets ARCH, BOARD, and
BOARD_NAME. Each Makefile applies board-specific compiler flags after its
arch block — pi5 gets Cortex-A76 tuning, pi4 gets Cortex-A72, qemu uses
portable x86-64 baseline instead of -march=native. Zynq-7020 is stubbed
in comments for future 32-bit ARM support. ARCH= override still works
for raw arch selection without a named board.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>