Switch to GPT partition format.

Switch to GPT partition format.

This changes switches to using the GPT partition format.
The GPT format is more modern and flexible. It allows us
to create up to 128 partitions, has a crc on the partition
table data, and has a backup partition. It should also make
it easier for us to incorporate a boot loader directly in
firmware (if we use EFI) since GPT is the recommended format.

The image_to_usb and chromeos_install scripts have been
modified to use a common set of shell functions to create
a bootable image. The common functions can create a bootable
image given a rootfs or rootfs partition with output to a
file or device. This simplifies image_to_usb and the
installer while at the same time keeps the code to create
a bootable image from a rootfs in one place. We also allow
for setting the size of the stateful partition. The 
default for a minimal partition setup allows us to use
smaller USB keyfobs as an output target if we want.

The work of partitioning is done by calling the bsd-ported
gpt partitioning utility, which works on a file or device.

In order to support legacy BIOS on x86, we use the
syslinux gpt "New protocol" with gptmbr.bin. See the
gpt.txt file in the syslinux doc directory.

[adlr, 2009-12-11 22:23:18]

http://codereview.chromium.org/445002/diff/1/2
File src/platform/installer/chromeos_install.sh (right):

http://codereview.chromium.org/445002/diff/1/2#newcode9
src/platform/installer/chromeos_install.sh:9: echo ""
do you want to check if the user is not root?

http://codereview.chromium.org/445002/diff/1/3
File src/platform/installer/chromeos_install_functions.sh (right):

http://codereview.chromium.org/445002/diff/1/3#newcode119
src/platform/installer/chromeos_install_functions.sh:119: if [ -e "$dest" ] ;
then
perhaps exit 1 or print error message if ! -e "$dest"

http://codereview.chromium.org/445002/diff/1/3#newcode239
src/platform/installer/chromeos_install_functions.sh:239: bs=1 count=15
conv=notrunc
s/15/$((label_field_length - 1))/

[adlr, 2009-12-17 08:17:52]

LGTM w/ comment

http://codereview.chromium.org/445002/diff/3002/3007
File src/scripts/build_image.sh (right):

http://codereview.chromium.org/445002/diff/3002/3007#newcode268
src/scripts/build_image.sh:268: # Copy utilities needed to create a bootable
image to the output directory.
would it be easier (or more future proof?) to just copy the whole scripts
directory?