This generates a minimal initial ramdisk for a Pixel C that simply mounts the root filesystem and switches to it.
To use, simply exec:
./mkinitramfs.sh
You will need a firmware_all.tar.gz in the current directory. You can get it
by running this.
You can also provide a custom path to it as well as other useful things, run
the script with -h for more detailed information.
The script will automatically fetch an appropriate Busybox binary.