boulder/draft: Default to autotools on unhandled build system

This will most likely be the closest match, plus we write out the recipe
file unconditionally then much to deangst to our packagers.

boulder/src/draft.rs

@@ -9,6 +9,7 @@ use fs_err as fs;
 use itertools::Itertools;
 use moss::Dependency;
 use thiserror::Error;
+use tui::Styled;
 use url::Url;
 
 use crate::util;
@@ -54,9 +55,13 @@ impl Drafter {
         // Remove temp extract dir
         fs::remove_dir_all(extract_root)?;
 
-        let Some(build_system) = build.detected_system else {
-            return Err(Error::UnhandledBuildSystem);
-        };
+        let build_system = build.detected_system.unwrap_or_else(|| {
+            println!(
+                "{} | Unhandled build system! - Defaulting to autotools",
+                "Warning".yellow()
+            );
+            build::System::Autotools
+        });
 
         let builddeps = builddeps(build.dependencies);
         let environment = build_system
@@ -125,8 +130,6 @@ impl File<'_> {
 
 #[derive(Debug, Error)]
 pub enum Error {
-    #[error("Unhandled build system")]
-    UnhandledBuildSystem,
     #[error("analyzing build system")]
     AnalyzeBuildSystem(#[source] build::Error),
     #[error("upstream")]