Support /product partition

This CL adds the following build flags to support building product partition
from Android build system.
- BOARD_AVB_PRODUCT_ADD_HASHTREE_FOOTER_ARGS
- BOARD_AVB_PRODUCT_KEY_PATH
- BOARD_AVB_PRODUCT_ALGORITHM
- BOARD_AVB_PRODUCT_ROLLBACK_INDEX_LOCATION
- BOARD_PREBUILT_PRODUCTIMAGE
- BOARD_PRODUCTIMAGE_EXTFS_INODE_COUNT
- BOARD_PRODUCTIMAGE_FILE_SYSTEM_TYPE
- BOARD_PRODUCTIMAGE_PARTITION_SIZE
- BOARD_PRODUCTIMAGE_SQUASHFS_BLOCK_SIZE
- BOARD_PRODUCTIMAGE_SQUASHFS_COMPRESSOR
- BOARD_PRODUCTIMAGE_SQUASHFS_COMPRESSOR_OPT
- BOARD_PRODUCTIMAGE_SQUASHFS_DISABLE_4K_ALIGN
- BOARD_USES_PRODUCTIMAGE
- LOCAL_PRODUCT_MODULE
- PRODUCT_FOOTER_ARGS
- PRODUCT_PRODUCT_BASE_FS_PATH
- PRODUCT_PRODUCT_VERITY_PARTITION
- TARGET_COPY_OUT_PRODUCT
- TARGET_OUT_PRODUCT*

And PRODUCT_PRODUCT_PROPERTIES is added to save product-specific
properties in /product/build.prop.

Bug: 64195575
Test: succeeded building product.img with BOARD_PRODUCTIMAGE_PARTITION_SIZE,
BOARD_PRODUCTIMAGE_FILE_SYSTEM_TYPE and PRODUCT_PRODUCT_VERITY_PARTITION.

Change-Id: I774e6a38003734421591e51bed103802ff84f432
diff --git a/core/main.mk b/core/main.mk
index 93c8d3b..98f6ecb 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -1041,6 +1041,9 @@
 .PHONY: vendorimage
 vendorimage: $(INSTALLED_VENDORIMAGE_TARGET)
 
+.PHONY: productimage
+productimage: $(INSTALLED_PRODUCTIMAGE_TARGET)
+
 .PHONY: systemotherimage
 systemotherimage: $(INSTALLED_SYSTEMOTHERIMAGE_TARGET)
 
@@ -1064,9 +1067,11 @@
 	$(INSTALLED_CACHEIMAGE_TARGET) \
 	$(INSTALLED_BPTIMAGE_TARGET) \
 	$(INSTALLED_VENDORIMAGE_TARGET) \
+	$(INSTALLED_PRODUCTIMAGE_TARGET) \
 	$(INSTALLED_SYSTEMOTHERIMAGE_TARGET) \
 	$(INSTALLED_FILES_FILE) \
 	$(INSTALLED_FILES_FILE_VENDOR) \
+	$(INSTALLED_FILES_FILE_PRODUCT) \
 	$(INSTALLED_FILES_FILE_SYSTEMOTHER) \
 	soong_docs
 
@@ -1132,6 +1137,7 @@
     $(COVERAGE_ZIP) \
     $(INSTALLED_FILES_FILE) \
     $(INSTALLED_FILES_FILE_VENDOR) \
+    $(INSTALLED_FILES_FILE_PRODUCT) \
     $(INSTALLED_FILES_FILE_SYSTEMOTHER) \
     $(INSTALLED_BUILD_PROP_TARGET) \
     $(BUILT_TARGET_FILES_PACKAGE) \