Turn on --fast on official builds.

parallel_emerge

 #!/usr/bin/python2.6
 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Program to run emerge in parallel, for significant speedup.
 
 Usage:
  ./parallel_emerge [--board=BOARD] [--workon=PKGS] [--no-workon-deps]
                    [--force-remote-binary=PKGS] [emerge args] package
@@ skipping 292 matching lines @@
       board_no_variant = self.board.split('_')[0]
       f = open(toolchain_path % (scripts_dir, board_no_variant))
       os.environ["CHOST"] = f.readline().strip()
       f.close()
 
       # Although CHROMEOS_ROOT isn't specific to boards, it's normally setup
       # inside emerge-${BOARD}, so we set it up here for compatibility. It
       # will be going away soon as we migrate to CROS_WORKON_SRCROOT.
       os.environ.setdefault("CHROMEOS_ROOT", os.environ["HOME"] + "/trunk")
 
-      # Modify the environment to disable locking by default.
-      # TODO(davidjames): This option can cause problems if packages muck
-      # with each other during the post-install step. There are a few host
-      # packages that do this, so we only do this environment modification for
-      # board builds.
-      os.environ.setdefault("PORTAGE_LOCKS", "false")
-
     # Turn off interactive delays
     os.environ["EBEEP_IGNORE"] = "1"
     os.environ["EPAUSE_IGNORE"] = "1"
     os.environ["UNMERGE_DELAY"] = "0"
 
     # Parse the emerge options.
     action, opts, cmdline_packages = parse_opts(emerge_args)
 
     # If we're installing to the board, we want the --root-deps option so that
     # portage will install the build dependencies to that location as well.
@@ skipping 20 matching lines @@
     # packages that own the same file. The collision-protect feature is more
     # strict, and less useful: it fails if it finds a conflicting file, even
     # if that file was created by an earlier ebuild that failed to install.
     #
     # We want to disable collision-protect here because we don't handle
     # failures during the merge step very well. Sometimes we leave old files
     # lying around and they cause problems, so for now we disable the flag.
     # TODO(davidjames): Look for a better solution.
     features = os.environ.get("FEATURES", "") + " -collision-protect"
 
-    # If we're cross-compiling, updating the environment every time we install
-    # a package isn't necessary, and leads to race conditions when
-    # PORTAGE_LOCKS is false. In this case, do environment updates at the end,
-    # instead.
-    if self.board and os.environ.get("PORTAGE_LOCKS") == "false":
+    # If we're installing packages to the board, and we're not using the
+    # official flag, we can enable the following optimizations:
+    #  1) Don't lock during install step. This allows multiple packages to be
+    #     installed at once. This is safe because our board packages do not
+    #     muck with each other during the post-install step.
+    #  2) Don't update the environment until the end of the build. This is
+    #     safe because board packages don't need to run during the build --
+    #     they're cross-compiled, so our CPU architecture doesn't support them
+    #     anyway.
+    if self.board and os.environ.get("CHROMEOS_OFFICIAL") != "1":
+      os.environ.setdefault("PORTAGE_LOCKS", "false")
       features = features + " no-env-update"
 
     os.environ["FEATURES"] = features
 
     # Now that we've setup the necessary environment variables, we can load the
     # emerge config from disk.
     settings, trees, mtimedb = load_emerge_config()
 
     # Check whether our portage tree is out of date. Typically, this happens
     # when you're setting up a new portage tree, such as in setup_board and
@@ skipping 1461 matching lines @@
   # need to upgrade the rest of the packages. So we'll go ahead and do that.
   if portage_upgrade:
     args = sys.argv[1:] + ["--nomerge=sys-apps/portage"]
     os.execvp(os.path.realpath(sys.argv[0]), args)
 
   print "Done"
   sys.exit(0)
 
 if __name__ == "__main__":
   main()