build_image: Add a -r alias for --noenable_rootfs_verification

It is annoying to have to type such a long flag and remember that is has
underscores, etc. Add a short-form flag.

BUG=chromium:798771
TEST=manually try it with the following change:
  # Parse command line.
  FLAGS "$@" || exit 1
  echo flags ${FLAGS_enable_rootfs_verification}
  exit 1

$ ./build_image -r
  --[no]enable_bootcache:  Default all bootloaders to NOT use boot cache. (default: false)
  -r,--[no]enable_rootfs_verification:  Default all bootloaders to use kernel-based root fs integrity checking.
                                        (default: true)
$ ./build_image --board=grunt test -r
flags 1
$ /build_image --board=grunt test --noenable_rootfs_verification
flags 1
$ ./build_image --board=grunt test
flags 0

Change-Id: Ie2c8ad320ffc5bbab3401fdcec6905fa4222e618
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/951702
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed