Added command line and environment to the hermit entry parameters

[jounathaen]

I'd like to get rid of the hypercalls in uhyve just to retrieve the env and argv. I think it makes sense to add them to the boot information, as they are available at boot time anyway.

(Once implemented in uhyve and hermit, this would solve hermit-os/uhyve#35)

[mkroening]

As we are slowly moving away from raw structs and towards device trees (#5), this should be done via the already available HardwareInfo::device_tree.

I think /chosen/bootargs would fit quite well:

chosen {
    bootargs = "env=RUST_LOG=info env=FOO=bar [OTHER_KERNEL_ARGS] -- [APP_ARGS]";
}

[jounathaen]

I think that is a good approach, but it should be considered that we potentially pass hundreds of environment variables.

As changing uhyve to use device trees is a bigger project, maybe we can still go with this approach as an intermediate step? (To at get rid of the hypercall first)

[mkroening]

I'd like to avoid having to do a entry version jump for this.

I think gradual migration should be easy. I'll open a draft PR tomorrow for initial device tree support for Uhyve, just for bootargs.