Set up initial structure for the nix builder.

src/command/build/mod.rs

@@ -0,0 +1,3 @@
+mod runner;
+
+pub(crate) use runner::run_build;

src/command/build/runner.rs

@@ -0,0 +1,29 @@
+use crate::cli::parameters::BuildArgs;
+use crate::config::Config;
+use crate::config::TargetConfig;
+use crate::error::CustomError;
+
+pub(crate) async fn run_build(args: BuildArgs) -> Result<(), CustomError> {
+    println!("{:?}", args);
+    let config = Config::load_from_file(args.config).await?;
+    println!("{:?}", config);
+
+    for target_name in args.target {
+        let target_config = {
+            let target_config = config.get_target_config(&target_name)?;
+            if let Some(conf) = target_config {
+                conf
+            } else {
+                return Err(format!("Could not find target {}", target_name).into());
+            }
+        };
+
+        prepare_flake_repo(target_config).await?;
+    }
+
+    Ok(())
+}
+
+async fn prepare_flake_repo(target_config: &TargetConfig) -> Result<(), CustomError> {
+    todo!()
+}