ota_from_target_files: Add an option to not sign OTA packages

Sometimes it is useful to be able to tell ota_from_target_files
to not sign the output zip file. For instance, the private
release key may not be available when ota_from_target_files
is executed; similarly the release tools may not be available
or executable where the private key is stored.

This change adds an option, '--no_signing', to simply output the
unsigned OTA zip file, instead of spuriously signing it with the
test key even though the zip file would need to be re-signed later
with a different key.

Change-Id: I1f3c4dc8ffa35ce85478f848b147aff3d40fe283

tools/releasetools/ota_from_target_files

@@ -88,6 +88,7 @@ OPTIONS.omit_prereq = False
 OPTIONS.extra_script = None
 OPTIONS.aslr_mode = True
 OPTIONS.worker_threads = 3
+OPTIONS.no_signing = False
 
 def MostPopularKey(d, default):
   """Given a dict, return the key corresponding to the largest
@@ -822,6 +823,8 @@ def main(argv):
         OPTIONS.aslr_mode = False
     elif o in ("--worker_threads"):
       OPTIONS.worker_threads = int(a)
+    elif o in ("--no_signing"):
+      OPTIONS.no_signing = True
     else:
       return False
     return True
@@ -836,6 +839,7 @@ def main(argv):
                                               "extra_script=",
                                               "worker_threads=",
                                               "aslr_mode=",
+                                              "no_signing",
                                               ],
                              extra_option_handler=option_handler)
 
@@ -870,9 +874,12 @@ def main(argv):
     OPTIONS.device_specific = os.path.normpath(OPTIONS.device_specific)
     print "using device-specific extensions in", OPTIONS.device_specific
 
-  temp_zip_file = tempfile.NamedTemporaryFile()
-  output_zip = zipfile.ZipFile(temp_zip_file, "w",
-                               compression=zipfile.ZIP_DEFLATED)
+  if OPTIONS.no_signing:
+    output_zip = zipfile.ZipFile(args[1], "w", compression=zipfile.ZIP_DEFLATED)
+  else:
+    temp_zip_file = tempfile.NamedTemporaryFile()
+    output_zip = zipfile.ZipFile(temp_zip_file, "w",
+                                 compression=zipfile.ZIP_DEFLATED)
 
   if OPTIONS.incremental_source is None:
     WriteFullOTAPackage(input_zip, output_zip)
@@ -896,8 +903,9 @@ def main(argv):
 
   output_zip.close()
 
-  SignOutput(temp_zip_file.name, args[1])
-  temp_zip_file.close()
+  if not OPTIONS.no_signing:
+    SignOutput(temp_zip_file.name, args[1])
+    temp_zip_file.close()
 
   common.Cleanup()