Support custom APEX signing tool

When an APEX specifies its custom signing tool (custom_sign_tool:),
apexkeys.txt contains the info and sign_target_files_apks pass the value
to apex_util.

For now the Virt APEX has its own custom signing tool (sign_virt_apex),
which is added to OTATOOLS.

Bug: 193504286
Test: sign_target_files_apks invokes sign_virt_apex
Change-Id: Iba845723fe3e18f542963324b9c58cd00914c5ba
diff --git a/tools/releasetools/test_sign_target_files_apks.py b/tools/releasetools/test_sign_target_files_apks.py
index ad9e657..92dca9a 100644
--- a/tools/releasetools/test_sign_target_files_apks.py
+++ b/tools/releasetools/test_sign_target_files_apks.py
@@ -328,23 +328,23 @@
         'Apex3.apex' : 'key3',
     }
     apex_keys = {
-        'Apex1.apex' : ('payload-key1', 'container-key1'),
-        'Apex2.apex' : ('payload-key2', 'container-key2'),
+        'Apex1.apex' : ('payload-key1', 'container-key1', None),
+        'Apex2.apex' : ('payload-key2', 'container-key2', None),
     }
     with zipfile.ZipFile(input_file) as input_zip:
       CheckApkAndApexKeysAvailable(input_zip, apk_key_map, None, apex_keys)
 
       # Fine to have both keys as PRESIGNED.
-      apex_keys['Apex2.apex'] = ('PRESIGNED', 'PRESIGNED')
+      apex_keys['Apex2.apex'] = ('PRESIGNED', 'PRESIGNED', None)
       CheckApkAndApexKeysAvailable(input_zip, apk_key_map, None, apex_keys)
 
       # Having only one of them as PRESIGNED is not allowed.
-      apex_keys['Apex2.apex'] = ('payload-key2', 'PRESIGNED')
+      apex_keys['Apex2.apex'] = ('payload-key2', 'PRESIGNED', None)
       self.assertRaises(
           AssertionError, CheckApkAndApexKeysAvailable, input_zip, apk_key_map,
           None, apex_keys)
 
-      apex_keys['Apex2.apex'] = ('PRESIGNED', 'container-key1')
+      apex_keys['Apex2.apex'] = ('PRESIGNED', 'container-key1', None)
       self.assertRaises(
           AssertionError, CheckApkAndApexKeysAvailable, input_zip, apk_key_map,
           None, apex_keys)
@@ -475,10 +475,10 @@
     self.assertEqual({
         'apex.apexd_test.apex': (
             'system/apex/apexd/apexd_testdata/com.android.apex.test_package.pem',
-            'build/make/target/product/security/testkey'),
+            'build/make/target/product/security/testkey', None),
         'apex.apexd_test_different_app.apex': (
             'system/apex/apexd/apexd_testdata/com.android.apex.test_package_2.pem',
-            'build/make/target/product/security/testkey'),
+            'build/make/target/product/security/testkey', None),
         }, keys_info)
 
   def test_ReadApexKeysInfo_mismatchingContainerKeys(self):
@@ -514,10 +514,10 @@
     self.assertEqual({
         'apex.apexd_test.apex': (
             'system/apex/apexd/apexd_testdata/com.android.apex.test_package.pem',
-            'build/make/target/product/security/testkey'),
+            'build/make/target/product/security/testkey', None),
         'apex.apexd_test_different_app.apex': (
             'system/apex/apexd/apexd_testdata/com.android.apex.test_package_2.pem',
-            'build/make/target/product/security/testkey'),
+            'build/make/target/product/security/testkey', None),
         }, keys_info)
 
   def test_ReadApexKeysInfo_missingPayloadPublicKey(self):
@@ -537,10 +537,10 @@
     self.assertEqual({
         'apex.apexd_test.apex': (
             'system/apex/apexd/apexd_testdata/com.android.apex.test_package.pem',
-            'build/make/target/product/security/testkey'),
+            'build/make/target/product/security/testkey', None),
         'apex.apexd_test_different_app.apex': (
             'system/apex/apexd/apexd_testdata/com.android.apex.test_package_2.pem',
-            'build/make/target/product/security/testkey'),
+            'build/make/target/product/security/testkey', None),
         }, keys_info)
 
   def test_ReadApexKeysInfo_presignedKeys(self):
@@ -560,10 +560,10 @@
     self.assertEqual({
         'apex.apexd_test.apex': (
             'system/apex/apexd/apexd_testdata/com.android.apex.test_package.pem',
-            'build/make/target/product/security/testkey'),
+            'build/make/target/product/security/testkey', None),
         'apex.apexd_test_different_app.apex': (
             'system/apex/apexd/apexd_testdata/com.android.apex.test_package_2.pem',
-            'build/make/target/product/security/testkey'),
+            'build/make/target/product/security/testkey', None),
         }, keys_info)
 
   def test_ReadApexKeysInfo_presignedKeys(self):
@@ -583,10 +583,10 @@
     self.assertEqual({
         'apex.apexd_test.apex': (
             'system/apex/apexd/apexd_testdata/com.android.apex.test_package.pem',
-            'build/make/target/product/security/testkey'),
+            'build/make/target/product/security/testkey', None),
         'apex.apexd_test_different_app.apex': (
             'system/apex/apexd/apexd_testdata/com.android.apex.test_package_2.pem',
-            'build/make/target/product/security/testkey'),
+            'build/make/target/product/security/testkey', None),
         }, keys_info)
 
   def test_ReplaceGkiSigningKey(self):