Cleanup package dependencies, incremental build and unit testing scripts

* Removed stale dependency / use of fakeroot unit test invocation.

* Separated incremental build and unit test invocation from
  gen_coverage_html.sh into their own scripts.

* Added checks for required binaries in gen_coverage_html.sh.

* Renamed setup_dev_packages to have a .sh suffix, for uniformity. Also
  requires that it installs packages regardless of whether or not
  they're already installed; this is to prevent a situation where
  packages were removed from the portage tree but happen to still live
  in the local chroot, so the discrepancy goes unnoticed (for example,
  sys-apps/fakeroot and dev-util/lcov).

* Cosmetics: switched to long options when applicable, for clarity.

BUG=None
TEST=Update engine builds, tests, and coverage generation correctly
invoked

CQ-DEPEND=I949f6b4abad52d04245e5982ac95884d1d0a05fc

Change-Id: I439e74eb9772f8f368256a0adf13503e3257e66c
Reviewed-on: https://gerrit.chromium.org/gerrit/23229
Reviewed-by: Gilad Arnold <garnold@chromium.org>
Tested-by: Gilad Arnold <garnold@chromium.org>
Commit-Ready: Gilad Arnold <garnold@chromium.org>
diff --git a/setup_dev_packages b/setup_dev_packages
index 64d063e..4ea2069 100755
--- a/setup_dev_packages
+++ b/setup_dev_packages
@@ -1,12 +1,15 @@
 #!/bin/bash
 
-# Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+# Copyright (c) 2012 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.
 
+# Emerges necessary packages for building and testing the update engine. This
+# allows incremental building, bypassing ebuild dependency resolution.
+
 set -ex
 
-sudo USE="-crash cros-debug" emerge -DNauv1 \
+sudo USE="-crash cros-debug" emerge -DNuv1 --selective=n "$@" \
   chromeos-base/hard-host-depends \
   chromeos-base/libchrome \
   chromeos-base/metrics \
@@ -15,5 +18,4 @@
   dev-cpp/gtest \
   dev-util/bsdiff \
   dev-util/lcov \
-  sys-apps/fakeroot \
   sys-apps/rootdev