Export attestation file information to provenance metadata of an artifact if its attestation file exists.

Bug: 231239599
Test: m provenance_metadata
Test: atest --host gen_provenance_metadata_test
Change-Id: I6c53d7713874c9b2fd8a422b030b7c8d23317f5b
diff --git a/provenance/tools/gen_provenance_metadata.py b/provenance/tools/gen_provenance_metadata.py
index b33f911..f3f4d1f 100644
--- a/provenance/tools/gen_provenance_metadata.py
+++ b/provenance/tools/gen_provenance_metadata.py
@@ -16,6 +16,7 @@
 
 import argparse
 import hashlib
+import os.path
 import sys
 
 import google.protobuf.text_format as text_format
@@ -51,6 +52,11 @@
     h.update(artifact_file.read())
   provenance_metadata.artifact_sha256 = h.hexdigest()
 
+  Log("Check if there is attestation for the artifact")
+  attestation_file_name = args.artifact_path + ".intoto.jsonl"
+  if os.path.isfile(attestation_file_name):
+    provenance_metadata.attestation_path = attestation_file_name
+
   text_proto = [
       "# proto-file: build/soong/provenance/proto/provenance_metadata.proto",
       "# proto-message: ProvenanceMetaData",