auto merge of #8789 : pnkfelix/rust/fsk-fix-typo-in-rust-mode.el, r=pnkfelix

Fix #6887.  (or rather, a bug injected by my prior commit for fixing that bug.)

src/etc/emacs/rust-mode.el

@@ -229,7 +229,7 @@ The initializer is `DEFAULT-TAB-WIDTH'.")
 ;; regexp (which is broken on a few edge cases), add our own 'rust
 ;; compilation error regexp and use it instead.
 (defvar rustc-compilation-regexps
-  (let ((file "^\\([^\n]+\\)")
+  (let ((file "\\([^\n]+\\)")
         (start-line "\\([0-9]+\\)")
         (start-col  "\\([0-9]+\\)")
         (end-line   "\\([0-9]+\\)")