[Issue] allow azd (via azure.yaml) to add —target to docker build

[splusq]

Describe the bug
Currently azure.yaml does not provide a mechanism to add a --target parameter to docker build. This is necessary for multi-stage docker build where there are multiple layers and at build time one decides which layer to target.

To Reproduce
Run azd package on a multi-stage docker file there are no options to pass the --target argument.

Expected behavior
If one were to build the docker file here's how one would pass the argument:

docker build --target foo -t docker.io/bar/baz -f foo/dockerfile .

Environment
Does not matter.

[rajeshkamal5050]

Does this already existing feature #2266 help achieve that? cc @vhvb1989 @wbreza

[Petermarcu]

--target is a different argument than what goes in buildargs.

I started a PR here that might be enough to unblock. I don't think its complete but could be a starting point.
#3052

[Petermarcu]

@splusq confirmed a build with my change worked for them.