Sort avb_custom_vbmeta_images_partition_list in misc_info.txt

This property is used as a dictionary in `releasetools/add_img_to_target_files.py`
and `releasetools/common.py`, so the order should not matter. Adding the
sort helps in diffing against the Soong built misc_info.txt

Test: presubmits
Bug: 398036609
Change-Id: I4f3def7543dbddeb3a68d840e4ecd876e1a9f282
diff --git a/core/Makefile b/core/Makefile
index f80ee8a..9e6893c 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -6048,7 +6048,7 @@
 	$(hide) echo "avb_vbmeta_vendor_rollback_index_location=$(BOARD_AVB_VBMETA_VENDOR_ROLLBACK_INDEX_LOCATION)" >> $@
 endif # BOARD_AVB_VBMETA_VENDOR_KEY_PATH
 ifneq (,$(strip $(BOARD_AVB_VBMETA_CUSTOM_PARTITIONS)))
-	$(hide) echo "avb_custom_vbmeta_images_partition_list=$(BOARD_AVB_VBMETA_CUSTOM_PARTITIONS)" >> $@
+	$(hide) echo "avb_custom_vbmeta_images_partition_list=$(sort $(BOARD_AVB_VBMETA_CUSTOM_PARTITIONS))" >> $@
 	$(hide) $(foreach partition,$(BOARD_AVB_VBMETA_CUSTOM_PARTITIONS),\
 	echo "avb_vbmeta_$(partition)=$(BOARD_AVB_VBMETA_$(call to-upper,$(partition)))" >> $@ ;\
 	echo "avb_vbmeta_$(partition)_args=$(BOARD_AVB_MAKE_VBMETA_$(call to-upper,$(partition))_IMAGE_ARGS)" >> $@ ;\