Add a "make reset" target that just removes the files created by preprocessing

Makefile

@@ -16,5 +16,9 @@ preproc.o: preproc.hpp mpcio.hpp types.hpp
 online.o: online.hpp mpcops.hpp coroutine.hpp
 mpcops.o: mpcops.hpp coroutine.hpp
 
-clean:
-	-rm -f $(BIN) $(OBJS) *.p[01].t*
+# Remove the files created by the preprocessing phase
+reset:
+	-rm -f *.p[01].t*
+
+clean: reset
+	-rm -f $(BIN) $(OBJS)