Fix to remove ext_XMS artifact from keytools Makefile. Caused mingw readdir error.

Author: dgarske

tools/keytools/Makefile

@@ -110,7 +110,6 @@ OBJS_VIRT=$(addprefix $(OBJDIR), $(notdir $(OBJS_REAL)))
 vpath %.c $(WOLFDIR)/wolfcrypt/src/
 vpath %.c $(WOLFBOOTDIR)/src/
 vpath %.c ./
-vpath %.c $(XMSSDIR)/
 
 .PHONY: clean all
 
@@ -127,9 +126,6 @@ $(OBJDIR)/%.o: $(WOLFBOOTDIR)/src/%.c
 $(OBJDIR)/%.o: $(WOLFDIR)/wolfcrypt/src/%.c
 	$(Q)$(CC) $(CFLAGS) -c -o $@ $<
 
-$(XMSSDIR)/src/%.o: $(XMSSDIR)/src/%.c
-	$(Q)$(CC) $(CFLAGS) -c -o $@ $<
-
 # build templates
 sign: $(OBJS_VIRT) $(LIBS) sign.o
 	@echo "Building signing tool"