Add sign_sepolicy_path for a binary to sign sepolicy.apex.

Bug: b/217570541
Test: sign_apex --container_key=testdata/testkey
--payload_key=testdata/testkey_RSA4096.key
--codename_to_api_level_map=S:31,T:32,UpsideDownCake:33
-e SEPolicy-33.zip=testdata/testkey com.android.sepolicy.apex
signed_sepolicy.apex

Change-Id: Ifdd1c6e7db07cbc4674450ab0e2226494c98605a
diff --git a/tools/releasetools/sign_apex.py b/tools/releasetools/sign_apex.py
index 6926467..d3e242b 100755
--- a/tools/releasetools/sign_apex.py
+++ b/tools/releasetools/sign_apex.py
@@ -52,6 +52,7 @@
 import common
 
 logger = logging.getLogger(__name__)
+OPTIONS = common.OPTIONS
 
 
 def SignApexFile(avbtool, apex_file, payload_key, container_key, no_hashtree,
@@ -70,7 +71,8 @@
       no_hashtree=no_hashtree,
       apk_keys=apk_keys,
       signing_args=signing_args,
-      sign_tool=sign_tool)
+      sign_tool=sign_tool,
+      is_sepolicy=apex_file.endswith(OPTIONS.sepolicy_name))
 
 
 def main(argv):