feat: mirror can set to none, set to rust when confit is none

src/config.rs

@@ -9,6 +9,15 @@ pub struct DockerBuildConfig {
     pub mirror: Option<String>,
 }
 
+pub fn load_docker_build_config_or_default() -> DockerBuildConfig {
+    load_docker_build_config().unwrap_or_else(|| {
+        DockerBuildConfig {
+            image: Some("rust".into()),
+            mirror: None,
+        }
+    })
+}
+
 pub fn load_docker_build_config() -> Option<DockerBuildConfig> {
     let config = find_docker_build_config_file()?;
     success!("Find config file: {:?}", config);