Resign apks contained in apex

Some apex payload images contain apk files. And these apks need to be
signed during the signing processed when sign_target_files_apks is
called. To support the signing, we can extract the payload and repack
the apex file with the (de)apexer tool. Add the signing support in the
apex_util.

Bug: 146508800
Test: unit tests pass, run sign_apex, sign_target_files_apks
Change-Id: If6d58975248709a144b07dbabf47c27916e5695e

tools/releasetools/test_sign_apex.py

@@ -41,3 +41,19 @@ class SignApexTest(test_utils.ReleaseToolsTestCase):
         container_key,
         False)
     self.assertTrue(os.path.exists(signed_foo_apex))
+
+  @test_utils.SkipIfExternalToolsUnavailable()
+  def test_SignApexWithApk(self):
+    test_apex = os.path.join(self.testdata_dir, 'has_apk.apex')
+    payload_key = os.path.join(self.testdata_dir, 'testkey_RSA4096.key')
+    container_key = os.path.join(self.testdata_dir, 'testkey')
+    apk_keys = {'wifi-service-resources.apk': os.path.join(
+        self.testdata_dir, 'testkey')}
+    signed_test_apex = sign_apex.SignApexFile(
+        'avbtool',
+        test_apex,
+        payload_key,
+        container_key,
+        False,
+        apk_keys)
+    self.assertTrue(os.path.exists(signed_test_apex))