fix help text, make bootup work for grub-pc

package/grub/Makefile

@@ -137,6 +137,7 @@ else
 	${CP} ${WRKINST}/usr/lib/grub/${GRUB_ARCH} \
 		$(IDIR_GRUB)/$(GRUB_DIR)
 	$(CP) ./files/$(GRUB_CFG) $(IDIR_GRUB)/$(GRUB_DIR)/grub.cfg
+	$(SED) "s/@@ROOTDEV@@/$(ADK_TARGET_ROOTDEV)/g" $(IDIR_GRUB)/$(GRUB_DIR)/grub.cfg
 endif
 	$(STAGING_HOST_DIR)/usr/bin/grub-mkimage \
 		-d $(WRKINST)/usr/lib/grub/$(GRUB_ARCH) \

target/x86_64/Makefile

@@ -90,10 +90,10 @@ endif
 ifeq ($(ADK_TARGET_FS),genimage)
 targethelp:
 	@echo "The disk image is: $(FW_DIR)/disk.img"
-	@echo "Use following command to install it on SD card:"
 ifeq ($(ADK_TARGET_QEMU),y)
 	@echo 'qemu-system-${QEMU_ARCH} ${QEMU_ARGS} $(FW_DIR)/disk.img'
 else
+	@echo "Use following command to install it on SD card:"
 	@echo 'sudo dd if=$(FW_DIR)/disk.img of=/dev/sdX bs=2048k'
 endif
 endif