Create EFI System Partition on USB image during build.

src/platform/installer/chromeos-install

 #!/bin/sh -u
 # 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.
 #
 # A script to install from removable media to hard disk.
 
 # Load functions and constants for chromeos-install.
 . "$(dirname "$0")/chromeos-common.sh" || exit 1
 . /usr/lib/shflags || exit 1
@@ skipping 165 matching lines @@
 
   sync
 }
 
 ##############################################################################
 
 # What do we expect & require to have on the source device?
 STATEFUL_IMG=${SRC}1
 KERNEL_IMG=${SRC}2
 ROOTFS_IMG=${SRC}3
+ESP_IMG=${SRC}4
 
 # Steal the PMBR code from the source MBR to put on the dest MBR, for booting
 # on legacy-BIOS devices.
 sudo dd if=$SRC of=$PMBRCODE bs=512 count=1
 
 # Create the GPT.
-install_gpt $FLAGS_dst $ROOTFS_IMG $KERNEL_IMG $STATEFUL_IMG $PMBRCODE
+install_gpt $FLAGS_dst $ROOTFS_IMG $KERNEL_IMG $STATEFUL_IMG $PMBRCODE $ESP_IMG
 
 if [ "$FLAGS_skip_rootfs" -eq "$FLAGS_TRUE" ]; then
   echo Done installing partitons.
   exit 0
 fi
 
 # Install the content.
 echo "Copying kernel..."
 sudo dd if=${KERNEL_IMG} of=${FLAGS_dst} conv=notrunc bs=512 \
   seek=${START_KERN_A}
 sudo dd if=${KERNEL_IMG} of=${FLAGS_dst} conv=notrunc bs=512 \
   seek=${START_KERN_B}
 
 echo "Copying rootfs..."
 install_rootfs ${ROOTFS_IMG} ${FLAGS_dst} ${START_ROOTFS_A} "H-ROOT-A"
 install_rootfs ${ROOTFS_IMG} ${FLAGS_dst} ${START_ROOTFS_B} "H-ROOT-B"
 
+echo "Copying ESP..."
+sudo dd if=${ESP_IMG} of=${DST} conv=notrunc bs=512 seek=${START_ESP}
+
 # We can't guarantee that the kernel will see the new partition table, so we
 # can't use it directly. We could force the kernel to reload it with an ioctl,
 # but then we might have the UI mounting and displaying any old filesystems
 # left over from the last install, and we don't want that either. So any access
 # that we need to do to the destination partitions will have to go through loop
 # devices.
 
 # Now run the postinstall script in each new rootfs. Note that even though
 # we're passing the new destination partition number as an arg, the postinst
 # script had better not try to access it, for the reasons we just gave.
@@ skipping 35 matching lines @@
 loop_offset_cleanup
 trap - EXIT
 
 # Force data to disk before we declare done.
 sync
 
 echo "------------------------------------------------------------"
 echo ""
 echo "Installation to '$FLAGS_dst' complete."
 echo "Please shutdown, remove the USB device, cross your fingers, and reboot."