Read default cfgs from rustc

crates/ra_project_model/src/json_project.rs

@@ -19,6 +19,8 @@ pub struct Crate {
     pub(crate) root_module: PathBuf,
     pub(crate) edition: Edition,
     pub(crate) deps: Vec<Dep>,
+    #[serde(default)]
+    pub(crate) features: Vec<String>,
 }
 
 #[derive(Clone, Copy, Debug, Deserialize)]