utility: add a simple tool for dumping the kernel config

Adds dump_kernel_config.c which takes in a file, reads it
all in to memory, then walks the blob until it can determine
the location of the kernel command line.

This is needed to allow the kernel config to inform legacy bootloader
configuration during autoupdates without packaging up dm-verity specific
options in some additional update metadata.

TEST=manual run over build_kernel_image.sh output

Review URL: http://codereview.chromium.org/2811029
2 files changed