lang/rust: run cargo commands from Cargo.toml dir

Instead of the current directory, which breaks file links in the
compilation buffer.

modules/lang/rust/autoload.el

@@ -6,3 +6,9 @@
 (defun +rust-cargo-project-p ()
   "Return t if this is a cargo project."
   (locate-dominating-file buffer-file-name "Cargo.toml"))
+
+;;;###autoload
+(defun +rust-cargo-compile (command)
+  "TODO"
+  (let ((default-directory (+rust-cargo-project-p)))
+    (compile command)))