This change adds two new targets to the Makefile.  Both make use of the
    `bootconfig` tool in the latest version of the SDK.  The first new
    target, `boot-config`, gives users the ability to create a properly
    formatted Boot Configuration initrd given a valid config file.  The
    second new target `validate-boot-config`, validates the Boot
    Configuration initrd, listing its contents.  If the initrd is somehow in
    a bad format, the tool will fail and print an error.

    The Makefile targets expect a valid configuration file in the root of
    the Bottlerocket repo named "bootconfig-input".  The Boot Configuration
    initrd will be created in the root of the repo with the name
    "bootconfig.data", which is what Bottlerocket expects the file to be
    named when using it.

$ cat bootconfig-input 
kernel {
    console = tty0, "ttyS1,115200n8"
}
init {
    systemd.log_level = debug
}

$ cargo make boot-config
...
[cargo-make] INFO - Running Task: boot-config
Creating a new boot config from input /home/fedora/bottlerocket/bottlerocket/bootconfig-input
Apply /tmp/bootconfig-input to /tmp/bootconfig.data
        Number of nodes: 8
        Size: 88 bytes
        Checksum: 6790
Boot configuration initrd may be found at /home/fedora/bottlerocket/bottlerocket/bootconfig.data
...

$ cargo make validate-boot-config
...
[cargo-make] INFO - Running Task: validate-boot-config
kernel.console = "tty0", "ttyS1,115200n8"
init.systemd.log_level = "debug"
...

$ cat bootconfig-input 
kernel {
    console = tty0
}

$ cargo make boot-config
...
Boot config exists at '/home/fedora/bottlerocket/bottlerocket/bootconfig.data', updating it with input /home/fedora/bottlerocket/bottlerocket/bootconfig-input
Apply /tmp/bootconfig-input to /tmp/bootconfig.data
        Number of nodes: 3
        Size: 31 bytes
        Checksum: 2360
Boot configuration initrd may be found at /home/fedora/bottlerocket/bottlerocket/bootconfig.data

$ cat bootconfig.data 
kernel {
    console = tty0
}
...

$ cargo make validate-boot-config
...
[cargo-make] INFO - Running Task: validate-boot-config
kernel.console = "tty0"