Waf: Modify build directory define if heli build command is given

Tools/ardupilotwaf/ap_library.py

@@ -139,7 +139,7 @@ def ap_library(bld, library, vehicle):
         kw.update(
             name=_vehicle_tgen_name(library, vehicle),
             source=source,
-            defines=ap.get_legacy_defines(vehicle),
+            defines=ap.get_legacy_defines(vehicle, bld),
             idx=_vehicle_index(vehicle),
         )
         bld.objects(**kw)

Tools/ardupilotwaf/ardupilotwaf.py

@@ -109,7 +109,16 @@ COMMON_VEHICLE_DEPENDENT_LIBRARIES = [
     'AP_FETtecOneWire',
 ]
 
-def get_legacy_defines(sketch_name):
+def get_legacy_defines(sketch_name, bld):
+    # If we are building heli, we adjust the build directory define so that 
+    # we do not need to actually split heli and copter directories
+    if bld.cmd == 'heli' or 'heli' in bld.targets:
+        return [
+        'APM_BUILD_DIRECTORY=APM_BUILD_Heli',
+        'SKETCH="' + sketch_name + '"',
+        'SKETCHNAME="' + sketch_name + '"',
+        ]
+
     return [
         'APM_BUILD_DIRECTORY=APM_BUILD_' + sketch_name,
         'SKETCH="' + sketch_name + '"',
@@ -253,7 +262,7 @@ def ap_program(bld,
         program_name = bld.path.name
 
     if use_legacy_defines:
-        kw['defines'].extend(get_legacy_defines(bld.path.name))
+        kw['defines'].extend(get_legacy_defines(bld.path.name, bld))
 
     kw['features'] = kw.get('features', []) + bld.env.AP_PROGRAM_FEATURES