waf: include piccolocan protocol directory in all libraries

with can_mgr in AP_Vehicle, eliding no longer works for the symbols generated from this directory, as *all* vehicles now get can, including the ones especially created in examples.  So now we include the symbols.

Tools/ardupilotwaf/ardupilotwaf.py

@@ -238,6 +238,7 @@ def ap_get_all_libraries(bld):
             continue
         libraries.append(name)
     libraries.extend(['AP_HAL', 'AP_HAL_Empty'])
+    libraries.append('AP_PiccoloCAN/piccolo_protocol')
     return libraries
 
 @conf