px4: added ARDUPILOT_BUILD=1 to PX4 build

this allows us to not include some source files in PX4Firmware modules

mk/px4_targets.mk

@@ -52,7 +52,7 @@ export GIT_SUBMODULES_ARE_EVIL = 1
 PYTHONPATH=$(SKETCHBOOK)/mk/PX4/Tools/genmsg/src:$(SKETCHBOOK)/mk/PX4/Tools/gencpp/src
 export PYTHONPATH
 
-PX4_MAKE = $(v) GIT_SUBMODULES_ARE_EVIL=1 make -C $(SKETCHBOOK) -f $(PX4_ROOT)/Makefile EXTRADEFINES="$(SKETCHFLAGS) $(WARNFLAGS) "'$(EXTRAFLAGS)' APM_MODULE_DIR=$(SKETCHBOOK) SKETCHBOOK=$(SKETCHBOOK) CCACHE=$(CCACHE) PX4_ROOT=$(PX4_ROOT) NUTTX_SRC=$(NUTTX_SRC) MAXOPTIMIZATION="-Os" UAVCAN_DIR=$(UAVCAN_DIR)
+PX4_MAKE = $(v) GIT_SUBMODULES_ARE_EVIL=1 ARDUPILOT_BUILD=1 make -C $(SKETCHBOOK) -f $(PX4_ROOT)/Makefile EXTRADEFINES="$(SKETCHFLAGS) $(WARNFLAGS) "'$(EXTRAFLAGS)' APM_MODULE_DIR=$(SKETCHBOOK) SKETCHBOOK=$(SKETCHBOOK) CCACHE=$(CCACHE) PX4_ROOT=$(PX4_ROOT) NUTTX_SRC=$(NUTTX_SRC) MAXOPTIMIZATION="-Os" UAVCAN_DIR=$(UAVCAN_DIR)
 PX4_MAKE_ARCHIVES = make -C $(PX4_ROOT) NUTTX_SRC=$(NUTTX_SRC) CCACHE=$(CCACHE) archives MAXOPTIMIZATION="-Os" 
 
 HASHADDER_FLAGS += --ardupilot "$(SKETCHBOOK)"