Use $(DIRSEP) not $(SLASH)

src/build/rules.mk

@@ -8,9 +8,9 @@ $(EXEODIR):
 	$(QUIET)$(IFNOTEXIST) mkdir $(EXEODIR)
 
 clean:
-	@echo Deleting $(OBJODIR)$(SLASH)
-	$(QUIET)$(DELETE) $(OBJODIR)$(SLASH)*
-	@echo Deleting $(LIBODIR)$(SLASH)
-	$(QUIET)$(DELETE) $(LIBODIR)$(SLASH)*
-	@echo Deleting $(EXEODIR)$(SLASH)
-	$(QUIET)$(DELETE) $(EXEODIR)$(SLASH)*
+	@echo Deleting $(OBJODIR)$(DIRSEP)
+	$(QUIET)$(DELETE) $(OBJODIR)$(DIRSEP)*
+	@echo Deleting $(LIBODIR)$(DIRSEP)
+	$(QUIET)$(DELETE) $(LIBODIR)$(DIRSEP)*
+	@echo Deleting $(EXEODIR)$(DIRSEP)
+	$(QUIET)$(DELETE) $(EXEODIR)$(DIRSEP)*