build: allow for slightly larger stack size on PX4

this allows building with gcc 4.9

mk/px4_targets.mk

@@ -80,6 +80,7 @@ else
 	$(v) echo "SRCS = $(wildcard $(SRCROOT)/*.cpp) $(SKETCHLIBSRCSRELATIVE)" >> $(SKETCHBOOK)/module.mk.new
 endif
 	$(v) echo "MODULE_STACKSIZE = 4096" >> $(SKETCHBOOK)/module.mk.new
+	$(v) echo "EXTRACXXFLAGS = -Wframe-larger-than=1200" >> $(SKETCHBOOK)/module.mk.new
 	$(v) cmp $(SKETCHBOOK)/module.mk $(SKETCHBOOK)/module.mk.new 2>/dev/null || mv $(SKETCHBOOK)/module.mk.new $(SKETCHBOOK)/module.mk
 	$(v) rm -f $(SKETCHBOOK)/module.mk.new