Add a command for cleaning up old targets.

src/cli/parameters.rs

@@ -18,6 +18,9 @@ pub(crate) enum Commands {
     /// Run a single build.
     Build(BuildArgs),
 
+    /// Clean up builds.
+    Clean(CleanArgs),
+
     /// Launch a daemon to run builds.
     Daemon(DaemonArgs),
 
@@ -36,6 +39,13 @@ pub(crate) struct BuildArgs {
     pub(crate) target: Vec<String>,
 }
 
+#[derive(Args, Debug)]
+pub(crate) struct CleanArgs {
+    /// Path to the nix_builder config file.
+    #[arg(short, long)]
+    pub(crate) config: PathBuf,
+}
+
 #[derive(Args, Debug)]
 pub(crate) struct DaemonArgs {
     /// Path to the nix_builder config file.