diff --git a/tools/build_aosp.py b/tools/build_aosp.py
index 0079554..b62ec02 100755
--- a/tools/build_aosp.py
+++ b/tools/build_aosp.py
@@ -26,7 +26,7 @@
       description = 'Checkout the AOSP source tree.')
   utils_aosp.add_common_arguments(parser)
   parser.add_argument('--tool',
-      choices = ['jack', 'd8', 'r8', 'default'],
+      choices = ['d8', 'r8', 'default'],
       default = 'd8',
       help='Compiler tool to use. Defaults to d8.')
   parser.add_argument('--mmm',
@@ -35,130 +35,51 @@
   parser.add_argument('--mmma',
       action = 'store_true',
       help='Use mmma instead of make')
-  parser.add_argument('--rebuild-system-image-after-mmm',
+  parser.add_argument('--show-commands',
       action = 'store_true',
-      help='Build the system image after building a package with mmm or mmma')
-  parser.add_argument('--clean-dex',
-      action = 'store_true',
-      help = 'Remove all dex files before the build. By default they'
-      " are removed only if '--tool=d8' and if they are older than the D8 tool")
+      help='Show commands executed during build.')
   parser.add_argument('-j',
       help='Projects to fetch simultaneously. ' +
       'Defaults to ' + str(J_DEFAULT) + '.',
       type=int,
-      default=J_DEFAULT)
+      default=-1)
   parser.add_argument('target', nargs='?')
   return parser.parse_args()
 
-def setup_and_clean_dex(aosp_root, tool, clean_dex):
-  print "Running AOSP build in " + aosp_root
+def build_aosp(aosp_root, lunch, make, tool,
+               concurrency, target, show_commands):
+  d8_option = 'USE_D8=false'
+  if tool == 'd8' or tool == 'r8' :
+    d8_option = 'USE_D8=true'
 
-  out = join(aosp_root, 'out')
-  utils.makedirs_if_needed(out)
-
-  # remove dex files older than the current d8 tool
-  counter = 0
-  if tool == 'd8' or clean_dex:
-    if not clean_dex:
-      d8jar_mtime = os.path.getmtime(utils.D8_JAR)
-    dex_files = (chain.from_iterable(glob(join(x[0], '*.dex'))
-      for x in os.walk(out)))
-    for f in dex_files:
-      if clean_dex or os.path.getmtime(f) <= d8jar_mtime:
-        os.remove(f)
-        counter += 1
-  if counter > 0:
-    print('Removed {} dex files.'.format(counter))
-
-PROGUARD_SCRIPT = """#!/bin/sh
-#
-# Start-up script for ProGuard -- free class file shrinker, optimizer,
-# obfuscator, and preverifier for Java bytecode.
-#
-# Note: when passing file names containing spaces to this script,
-#       you\'ll have to add escaped quotes around them, e.g.
-#       "\"/My Directory/My File.txt\""
-
-# Account for possibly missing/basic readlink.
-# POSIX conformant (dash/ksh/zsh/bash).
-PROGUARD=`readlink -f "$0" 2>/dev/null`
-if test "$PROGUARD" = \'\'
-then
-  PROGUARD=`readlink "$0" 2>/dev/null`
-  if test "$PROGUARD" = \'\'
-  then
-    PROGUARD="$0"
-  fi
-fi
-
-PROGUARD_HOME=`dirname "$PROGUARD"`/..
-
-# BEGIN android-changed Added -Xmx2G for Mac builds
-java -Xmx2G -jar "$PROGUARD_HOME/lib/proguard.jar" "$@"
-# END android-changed
-"""
-
-def prepare_for_proguard(aosp_root):
-  # Write the default proguard.sh script.
-  proguard_script = join(aosp_root, 'external', 'proguard', 'bin', 'proguard.sh')
-  with open(proguard_script, 'w') as f:
-    f.write(PROGUARD_SCRIPT)
-
-  os.chmod(proguard_script, S_IRWXU)
-
-def prepare_for_r8(aosp_root):
-  # Write the proguard.sh script invoking R8.
-  compat_proguard_jar = join(
-      utils.REPO_ROOT, 'build', 'libs', 'compatproguard.jar')
-  proguard_script = join(aosp_root, 'external', 'proguard', 'bin', 'proguard.sh')
-  with open(proguard_script, 'w') as f:
-    f.write('java -jar ' + compat_proguard_jar + ' "$@" --min-api 10000')
-  os.chmod(proguard_script, S_IRWXU)
-
-def build_aosp(aosp_root, lunch, make, tool, concurrency, target):
-  jack_option = 'ANDROID_COMPILE_WITH_JACK=' \
-      + ('true' if tool == 'jack' else 'false')
-
-  # DX_ALT_JAR need to be cleared if not set, for 'make' to work properly
-  alt_jar_option = 'DX_ALT_JAR='
-  if tool == 'd8':
-    alt_jar_option += utils.COMPATDX_JAR
-
+  r8_option = 'USE_R8=false'
   if tool == 'r8':
-    prepare_for_r8(aosp_root)
-    # Use D8 compatdx dexer with hack for forwarding the R8 dex file.
-    alt_jar_option += utils.COMPATDX_JAR
-  else:
-    prepare_for_proguard(aosp_root)
+    r8_option = 'USE_R8=true'
 
-  j_option = '-j' + str(concurrency);
-  print("-- Building Android image with '{} {} {} {}'." \
-    .format(make, j_option, jack_option, alt_jar_option))
+  j_option = '-j'
+  if concurrency > 0:
+    j_option += str(concurrency)
 
-  command = [make, j_option, jack_option, alt_jar_option]
+  command = [make, j_option]
+  if show_commands:
+    command.append('showcommands')
+  command.extend([d8_option, r8_option])
   if target:
     command.append(target)
 
+  print 'Building using: ' + ' '.join(command)
   utils_aosp.run_through_aosp_helper(lunch, command, aosp_root)
 
 def Main():
   args = parse_arguments()
 
-  # Build the required tools.
-  if args.tool == 'd8' or args.tool == 'r8':
-    gradle.RunGradle(['d8', 'r8', 'compatdx', 'compatproguard'])
-
-  setup_and_clean_dex(args.aosp_root, args.tool, args.clean_dex)
-
-  make = 'make'
+  make = 'm'
   if args.mmm:
     make = 'mmm'
   if args.mmma:
     make = 'mmma'
-  build_aosp(args.aosp_root, args.lunch, make, args.tool, args.j, args.target)
-  # Call make to re-build the system image if requested.
-  if args.rebuild_system_image_after_mmm and (args.mmm or args.mmma):
-    build_aosp(args.aosp_root, args.lunch, 'make', 'd8', args.j, None)
+  build_aosp(args.aosp_root, args.lunch, make, args.tool,
+             args.j, args.target, args.show_commands)
 
 if __name__ == '__main__':
   sys.exit(Main())