Moved debootstrap phase from build_image.sh to install_packages.sh.

Moved debootstrap phase from build_image.sh to install_packages.sh.

This puts all package installation for the rootfs in one place. It
also makes it so that you can run install_packages.sh --root="foo"
outside of the build_image.sh script if you want to test something
without going through the full image build. With this change
build_image basically:
 - Sets up a loopback mounted rootfs
 - Calls install_packages.sh on rootfs
 - Calls customize_rootfs on rootfs
 - Makes the rootfs bootable

[Bill Richardson, 2009-12-23 23:07:35]

http://codereview.chromium.org/520004/diff/1/3
File src/scripts/install_packages.sh (right):

http://codereview.chromium.org/520004/diff/1/3#newcode29
src/scripts/install_packages.sh:29: DEFINE_string output_dir "$(pwd)" \
Do we really want to default the output dir (and setup dir) to $(pwd) ? That's
almost always going to be src/scripts, which could really mess things up if we
forget to specify it.

http://codereview.chromium.org/520004/diff/1/3#newcode188
src/scripts/install_packages.sh:188: install "linux-image-${KERNEL_VERSION}"
The linux image gets left in src/build/x86/local_packages, just like any other
.deb. Can't we just add it to package-list-prod.txt, instead of searching for it
and adding it as a special case?

Same for bootchart, below.

[Bill Richardson, 2009-12-23 23:56:10]

LGTM