Revert #216 and Add Suggestions from #226

This reverts the `setq-local` for `compile-command` and replaces it
with a function which can be used to invoke compile with `"cargo
build"` as the compile command.

Author: iwillspeak

rust-mode.el

@@ -1491,6 +1491,11 @@ This is written mainly to be used as `end-of-defun-function' for Rust."
   (interactive)
   (setq-local rust-format-on-save nil))
 
+(defun rust-compile ()
+  "Compile using `cargo build`"
+  (interactive)
+  (compile "cargo build"))
+
 (defvar rust-mode-map
   (let ((map (make-sparse-keymap)))
     (define-key map (kbd "C-c C-f") 'rust-format-buffer)
@@ -1547,8 +1552,6 @@ This is written mainly to be used as `end-of-defun-function' for Rust."
   (setq-local parse-sexp-lookup-properties t)
   (setq-local electric-pair-inhibit-predicate 'rust-electric-pair-inhibit-predicate-wrap)
 
-  (setq-local compile-command "cargo build")
-
   (add-hook 'before-save-hook 'rust--before-save-hook nil t)
 
   (setq-local rust-buffer-project nil)