Reduce OTA tools's dependency on brillo_update_payload

brillo_update_payload is thin bash wrapper for delta_generator, and
OTA tools are wrappers around brillo_update_payload. This is
inconveinent, as adding a new flag requires changing 3 places. Since
brillo_update_payload is really thin, skip it and invoke delta_generator
directly.

Test: th
Bug: 293313353
Change-Id: I2fd5af95c571ea45aea62f9eec475f0f4e864953
diff --git a/tools/releasetools/ota_utils.py b/tools/releasetools/ota_utils.py
index 8993da9..9b3367e 100644
--- a/tools/releasetools/ota_utils.py
+++ b/tools/releasetools/ota_utils.py
@@ -897,30 +897,7 @@
     """
     assert isinstance(payload_signer, PayloadSigner)
 
-    # 1. Generate hashes of the payload and metadata files.
-    payload_sig_file = common.MakeTempFile(prefix="sig-", suffix=".bin")
-    metadata_sig_file = common.MakeTempFile(prefix="sig-", suffix=".bin")
-    cmd = ["brillo_update_payload", "hash",
-           "--unsigned_payload", self.payload_file,
-           "--signature_size", str(payload_signer.maximum_signature_size),
-           "--metadata_hash_file", metadata_sig_file,
-           "--payload_hash_file", payload_sig_file]
-    self._Run(cmd)
-
-    # 2. Sign the hashes.
-    signed_payload_sig_file = payload_signer.SignHashFile(payload_sig_file)
-    signed_metadata_sig_file = payload_signer.SignHashFile(metadata_sig_file)
-
-    # 3. Insert the signatures back into the payload file.
-    signed_payload_file = common.MakeTempFile(prefix="signed-payload-",
-                                              suffix=".bin")
-    cmd = ["brillo_update_payload", "sign",
-           "--unsigned_payload", self.payload_file,
-           "--payload", signed_payload_file,
-           "--signature_size", str(payload_signer.maximum_signature_size),
-           "--metadata_signature_file", signed_metadata_sig_file,
-           "--payload_signature_file", signed_payload_sig_file]
-    self._Run(cmd)
+    signed_payload_file = payload_signer.SignPayload(self.payload_file)
 
     self.payload_file = signed_payload_file