Move AVB related properties from 'system_other' to 'system'

The original CL in AOSP is for 'system' partition.
Howerver, after automerger merges the CL from aosp to goog gerrit, it
patches part of the properties to 'system_other' partition. Correct this by
moving the system_avb* properties to 'system'.

Bug: 31264226
Test: build aosp_angler-userdebug successfully
Change-Id: I1a7128d29c1152315e9b50cfe5bbe13b47b131a7
diff --git a/tools/releasetools/build_image.py b/tools/releasetools/build_image.py
index d727ddd..c51a80c 100755
--- a/tools/releasetools/build_image.py
+++ b/tools/releasetools/build_image.py
@@ -633,6 +633,9 @@
     copy_prop("system_squashfs_block_size", "squashfs_block_size")
     copy_prop("system_squashfs_disable_4k_align", "squashfs_disable_4k_align")
     copy_prop("system_base_fs_file", "base_fs_file")
+    copy_prop("system_avb_enable", "avb_enable")
+    copy_prop("system_avb_add_hashtree_footer_args",
+              "avb_add_hashtree_footer_args")
   elif mount_point == "system_other":
     # We inherit the selinux policies of /system since we contain some of its files.
     d["mount_point"] = "system"
@@ -646,9 +649,6 @@
     copy_prop("system_squashfs_compressor_opt", "squashfs_compressor_opt")
     copy_prop("system_squashfs_block_size", "squashfs_block_size")
     copy_prop("system_base_fs_file", "base_fs_file")
-    copy_prop("system_avb_enable", "avb_enable")
-    copy_prop("system_avb_add_hashtree_footer_args",
-              "avb_add_hashtree_footer_args")
   elif mount_point == "data":
     # Copy the generic fs type first, override with specific one if available.
     copy_prop("fs_type", "fs_type")