Add archive script that the bots can archive release versions

Move the path to d8 and r8 jar files into utils.

Bug:
Change-Id: Ibf584af6ba94c35a73829e87778a57984240e925
diff --git a/tools/d8.py b/tools/d8.py
index d214cf5..2510b75 100755
--- a/tools/d8.py
+++ b/tools/d8.py
@@ -9,8 +9,6 @@
 import sys
 import utils
 
-D8_JAR = os.path.join(utils.REPO_ROOT, 'build', 'libs', 'd8.jar')
-
 def run(args, build = True, debug = True, profile = False, track_memory_file=None):
   if build:
     gradle.RunGradle(['D8'])
@@ -22,10 +20,10 @@
     cmd.append('-ea')
   if profile:
     cmd.append('-agentlib:hprof=cpu=samples,interval=1,depth=8')
-  cmd.extend(['-jar', D8_JAR])
+  cmd.extend(['-jar', utils.D8_JAR])
   cmd.extend(args)
   utils.PrintCmd(cmd)
-  subprocess.check_call(cmd)
+  return subprocess.check_output(cmd)
 
 def main():
   build = True