Add quote to the signing arguments when passing to apexer

We should add quote when passing the signing arguments to apexer. So
the final argument whould look like
apexer ... --signing_args "--signing_helper_with_files=%path"

And the argument parser in avbtool will eventually parse the
"--signing_helper_with_files" correctly.

Bug: 148627666
Test: unittest pass, run a smoke sign_target_files_apk with signing arguments
Change-Id: Ie203d26a508cb98ca94e6c364a2640b681ad79f2

tools/releasetools/apex_utils.py

@@ -157,8 +157,10 @@ class ApexApkSigner(object):
                   os.getenv('PATH')]
     for key, val in arguments_dict.items():
       repack_cmd.extend(['--' + key, val])
+    # Add quote to the signing_args as we will pass
+    # --signing_args "--signing_helper_with_files=%path" to apexer
     if signing_args:
-      repack_cmd.extend(['--signing_args', signing_args])
+      repack_cmd.extend(['--signing_args', '"{}"'.format(signing_args)])
     # optional arguments for apex repacking
     manifest_json = os.path.join(apex_dir, 'apex_manifest.json')
     if os.path.exists(manifest_json):

tools/releasetools/test_apex_utils.py

@@ -189,7 +189,7 @@ class ApexUtilsTest(test_utils.ReleaseToolsTestCase):
 
     signing_helper = os.path.join(self.testdata_dir, 'signing_helper.sh')
     os.chmod(signing_helper, 0o700)
-    payload_signer_args = '--signing_helper_with_files {}'.format(
+    payload_signer_args = '--signing_helper_with_files={}'.format(
         signing_helper)
     signer.ProcessApexFile(apk_keys, self.payload_key, payload_pubkey,
                            payload_signer_args)