qmk_firmware_custom/keyboards/planck/keymaps/am/rules.mk

# Build Options
#   change to "no" to disable the options, or define them in the Makefile in
#   the appropriate keymap folder that will get included automatically
#
MOUSEKEY_ENABLE = yes       # Mouse keys(+4700)
EXTRAKEY_ENABLE = yes       # Audio control and System control(+450)
CONSOLE_ENABLE = no         # Console for debug(+400)
COMMAND_ENABLE = no         # Commands for debug and configuration
NKRO_ENABLE = yes           # Nkey Rollover - if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
AUDIO_ENABLE = yes          # Audio output on port C6