<command-line>:0:18: warning: "HAL_BOARD_LINUX" is not defined [-Wundef]
../../libraries/AP_Notify/Buzzer.h:20:5: note: in expansion of macro ‘CONFIG_HAL_BOARD’
#if CONFIG_HAL_BOARD == HAL_BOARD_VRBRAIN
^
In file included from ../../libraries/AP_Notify/Buzzer.cpp:18:0:
../../libraries/AP_Notify/Buzzer.h:20:25: warning: "HAL_BOARD_VRBRAIN" is not defined [-Wundef]
#if CONFIG_HAL_BOARD == HAL_BOARD_VRBRAIN
^
Due to the way the headers are organized changing a single change in
an AP_Notify driver would trigger a rebuild for most of the files in
the project. Time could be saved by using ccache (since most of the
things didn't change) but we can do better, i.e. re-organize the headers
so we don't have to re-build everything.