Add a --to option to build_image

src/scripts/build_gpt.sh

 #!/bin/bash
 #
 # 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.
 #
 # Load common constants.  This should be the first executable line.
 # The path to common.sh should be relative to your script's location.
 . "$(dirname "$0")/common.sh"
 
@@ skipping 126 matching lines @@
   PMBRCODE=$(readlink -f /usr/share/syslinux/gptmbr.bin)
 fi
 
 # Create the GPT. This has the side-effect of setting some global vars
 # describing the partition table entries (see the comments in the source).
 install_gpt $OUTDEV $ROOTFS_IMG $KERNEL_IMG $STATEFUL_IMG $PMBRCODE
 
 # Emit helpful scripts for testers, etc.
 ${SCRIPTS_DIR}/emit_gpt_scripts.sh "${OUTDEV}" "${IMAGEDIR}"
 
+sudo=
+if [ ! -w "$OUTDEV" ] ; then

[adlr, 2010/04/01 22:47:07]

maybe [ -b "$OUTDEV" ] is better?
-b means "it is a block device"

+  # use sudo when writing to a block device.
+  sudo=sudo
+fi
+
 # Now populate the partitions.
 echo "Copying stateful partition..."
-dd if=${STATEFUL_IMG} of=${OUTDEV} conv=notrunc bs=512 seek=${START_STATEFUL}
+$sudo dd if=${STATEFUL_IMG} of=${OUTDEV} conv=notrunc bs=512 \
+    seek=${START_STATEFUL}
 
 echo "Copying kernel..."
-dd if=${KERNEL_IMG} of=${OUTDEV} conv=notrunc bs=512 seek=${START_KERN_A}
-  
+$sudo dd if=${KERNEL_IMG} of=${OUTDEV} conv=notrunc bs=512 seek=${START_KERN_A}
+
 echo "Copying rootfs..."
-dd if=${ROOTFS_IMG} of=${OUTDEV} conv=notrunc bs=512 seek=${START_ROOTFS_A}
+$sudo dd if=${ROOTFS_IMG} of=${OUTDEV} conv=notrunc bs=512 seek=${START_ROOTFS_A}
 
 # Clean up temporary files.
 if [[ -n "${MBR_IMG:-}" ]]; then
   rm "${MBR_IMG}"
 fi