Dev flag is not used in customize_rootfs and we should not be making dev-specific changes there.

src/scripts/build_image

 #!/bin/bash
 
 # Copyright (c) 2009 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.
 
 # Script to build a bootable keyfob-based chromeos system image from within
 # a chromiumos setup. This assumes that all needed packages have been built into
 # the given target's root with binary packages turned on. This script will
 # build the Chrome OS image using only pre-built binary packages.
@@ skipping 324 matching lines @@
   sudo cp -a "$(which ldd)" "${ROOT_DEV_DIR}/usr/bin"
 fi
 
 # Install packages required for testing.
 if [[ $FLAGS_withtest -eq $FLAGS_TRUE ]] ; then
   sudo INSTALL_MASK="$INSTALL_MASK" emerge-${BOARD} \
       --root="$ROOT_DEV_DIR" --root-deps=rdeps \
       --usepkgonly chromeos-test $EMERGE_JOBS
 fi
 
-# Perform any customizations on the root file system that are needed.
-EXTRA_CUSTOMIZE_ROOTFS_FLAGS=""
-if [ $FLAGS_withdev -eq $FLAGS_TRUE ]; then
-  EXTRA_CUSTOMIZE_ROOTFS_FLAGS="--withdev"
-fi
-
 # Extract the kernel from the root filesystem for use by the GPT image. Legacy
 # BIOS will use the kernel in the rootfs (via syslinux), Chrome OS BIOS will
 # use the kernel partition.
 sudo cp -f "${ROOT_FS_DIR}/boot/vmlinuz" "${OUTPUT_DIR}/vmlinuz.image"
 
 # Create EFI System Partition to boot stock EFI BIOS (but not ChromeOS EFI
 # BIOS). We only need this for x86, but it's simpler and safer to keep the disk
 # images the same for both x86 and ARM.
 ESP_IMG=${OUTPUT_DIR}/esp.image
 # NOTE: The size argument for mkfs.vfat is in 1024-byte blocks. We'll hard-code
@@ skipping 38 matching lines @@
 # By default, dev mode should be activated for either development builds or
 # test builds.
 if [[ $FLAGS_withdev -eq $FLAGS_TRUE ]] ||\
     [[ $FLAGS_withtest -eq $FLAGS_TRUE ]]; then
   sudo touch "$ROOT_FS_DIR/root/.dev_mode"
 
   # Re-run ldconfig to fix /etc/ldconfig.so.cache.
   sudo /sbin/ldconfig -r "$ROOT_FS_DIR"
 fi
 
+# Perform any customizations on the root file system that are needed.
 "${SCRIPTS_DIR}/customize_rootfs" \
   --root="$ROOT_FS_DIR" \
   --target="$ARCH" \
-  --board="$BOARD" \
-  $EXTRA_CUSTOMIZE_ROOTFS_FLAGS
+  --board="$BOARD"
 
 # Check that the image has been correctly created.
 "${SCRIPTS_DIR}/test_image" \
   --root="$ROOT_FS_DIR" \
   --target="$ARCH"
 
 # Clean up symlinks so they work on a running target rooted at "/".
 # Here development packages are rooted at /usr/local.  However, do not
 # create /usr/local or /var on host (already exist on target).
 setup_symlinks_on_root "/usr/local" "/var"
@@ skipping 18 matching lines @@
 
 OUTSIDE_OUTPUT_DIR="../build/images/${FLAGS_board}/${IMAGE_SUBDIR}"
 echo "Done.  Image created in ${OUTPUT_DIR}"
 echo "To copy to USB keyfob, OUTSIDE the chroot, do something like:"
 echo "  ./image_to_usb.sh --from=${OUTSIDE_OUTPUT_DIR} --to=/dev/sdX"
 echo "To convert to VMWare image, OUTSIDE the chroot, do something like:"
 echo "  ./image_to_vmware.sh --from=${OUTSIDE_OUTPUT_DIR}"
 echo "from the scripts directory where you entered the chroot."
 
 trap - EXIT