add spm-module to complete command

[vdka]

Adds support for reading the build commands from the build.yaml file
closes #270

[jpsim]

Could you please add a changelog entry, following the guidelines in CONTRIBUTING.md?

It's also really unfortunate that we don't have SPM tests at the moment, but arguably out of scope for this PR.

[jpsim]

I don't think we should be mixing user-provided arguments with SPM-based ones. How's this instead?

var args: [String]
if !options.spmModule.isEmpty {
    guard let module = Module(spmName: options.spmModule) else {
        return .failure(.invalidArgument(description: "Bad module name"))
    }
    args = module.compilerArguments
} else {
    args = ["-c", path] + options.compilerargs
    if args.index(of: "-sdk") == nil {
        args.append(contentsOf: ["-sdk", sdkPath()])
    }
}

[vdka]

I have rebased onto the latest commit and made the changes suggested. Is there any documentation I need to update with this new flag?

[jpsim]

Is there any documentation I need to update with this new flag?

Could have updated the "Complete" section of the README, but that's unnecessary I think. Documentation in the changelog is sufficient IMO.

Thanks!