Set avb_hash_algorithm=sha256 for system & vendor img

This sets the hash_algorithm used in add_hashtree_footer to sha256
(which otherwise defaults to sha1).

Bug: 262892300
Test: (Using avbtool) Check the image_info microdroid.img &
microdroid_vendor.img

Change-Id: I4e17e38bd2d2c4ab0e2041c25ebde74c59e289cf
diff --git a/microdroid/Android.bp b/microdroid/Android.bp
index 2b8e03f..3141741 100644
--- a/microdroid/Android.bp
+++ b/microdroid/Android.bp
@@ -46,6 +46,7 @@
     use_avb: true,
     avb_private_key: ":microdroid_sign_key",
     avb_algorithm: "SHA256_RSA4096",
+    avb_hash_algorithm: "sha256",
     partition_name: "system",
     deps: [
         "init_second_stage",
@@ -213,6 +214,7 @@
     },
     avb_private_key: ":microdroid_sign_key",
     avb_algorithm: "SHA256_RSA4096",
+    avb_hash_algorithm: "sha256",
     file_contexts: ":microdroid_vendor_file_contexts.gen",
     // For deterministic output, use fake_timestamp, hard-coded uuid
     fake_timestamp: "1611569676",