Add sign_virt_apex_test

This test re-signs the virt apex contents and then check if they are
signed with the new key. Note that this isn't an end-to-end test to
install re-signed apex and see if it works, but only checks avbtool
signable items are signed with the new key by comparing pubkey digest.
This will help to notice when adding a new signed item without modifying
sign_virt_apex though.

Bug: 193504286
Test: atest --host sign_virt_apex_test
Change-Id: I16098c49f41e14f571dca272310b81459d9803a8
diff --git a/apex/sign_virt_apex_test.xml b/apex/sign_virt_apex_test.xml
new file mode 100644
index 0000000..5ea84a1
--- /dev/null
+++ b/apex/sign_virt_apex_test.xml
@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2021 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+<configuration description="Runs sign_virt_apex test">
+    <test class="com.android.tradefed.testtype.binary.ExecutableHostTest" >
+      <option name="binary" value="sign_virt_apex_test"/>
+    </test>
+</configuration>