build_binaries.py: print not-found-on-boardlist message

Makes it clearer in the output that we're skipping a board because it isn't in the configure list.  Currently it just does the submodule updaet then goes onto the next build, without telling you why it's not doing anything more

Tools/scripts/build_binaries.py

@@ -225,7 +225,10 @@ is bob we will attempt to checkout bob-AVR'''
                     line = line.replace("'", "")
                     line = line.replace(" ", "")
                     boards = line.split(",")
-                    return board not in boards
+                    ret = board not in boards
+                    if ret:
+                        self.progress("Skipping board (%s) - not in board list" % board)
+                    return ret
         except IOError as e:
             if e.errno != 2:
                 raise