Well, I just attempted this again, same problem is back.
pi@navio-rpi ~/ardupilot/ArduPlane $ make navio
// BUILDROOT=/tmp/ArduPlane.build HAL_BOARD=HAL_BOARD_LINUX HAL_BOARD_SUBTYPE=HAL_BOARD_SUBTYPE_LINUX_NAVIO TOOLCHAIN=RPI EXTRAFLAGS=-DGIT_VERSION="f486dd46"
building /tmp/ArduPlane.build/ArduPlane.cpp
%% ArduPlane.cpp
make: *** No rule to make target '/home/pi/ardupilot/libraries/GCS_MAVLink/include/mavlink/v1.0/ardupilotmega/../common/./mavlink_msg_scaled_imu3.h', needed by '/tmp/ArduPlane.build/ArduPlane.o'. Stop.
Would be great if someone can check the guide to see if there’s anything missing.
Further, I’m not sure why I can’t compile ArduPlane-release from the diydrones git. Same error as in OP (expected primary-expression before ‘.’ token) - saw somewhere else online this may be due to an old gcc, tried 4.9 and still the same issue.