build-system/emacs: Use 'emacs-minimal' by default.

* guix/build-system/emacs.scm (default-emacs): Use 'emacs-minimal'.
* gnu/packages/emacs.scm (emacs-auctex): Use 'emacs'.

gnu/packages/emacs.scm

@@ -1017,6 +1017,9 @@ as a library for other Emacs packages.")
         (base32
          "1pmki8hdjjikxlvip3pzi350bln3gcimr27yjf0xfwjvnp5hh9nc"))))
     (build-system emacs-build-system)
+    ;; We use 'emacs' because AUCTeX requires dbus at compile time
+    ;; ('emacs-minimal' does not provide dbus).
+    (arguments `(#:emacs ,emacs))
     (native-inputs
      `(("perl" ,perl)))
     (home-page "http://www.gnu.org/software/auctex/")

guix/build-system/emacs.scm

@@ -47,11 +47,7 @@
   "Return the default Emacs package."
   ;; Lazily resolve the binding to avoid a circular dependency.
   (let ((emacs-mod (resolve-interface '(gnu packages emacs))))
-    ;; we use 'emacs' instead of 'emacs-no-x' because the latter appears not
-    ;; to be loading some macros and causes problems to some packages.  For
-    ;; example, with the latter AUCTeX gives the error message:
-    ;; "(invalid-function dbus-ignore-errors)".
-    (module-ref emacs-mod 'emacs)))
+    (module-ref emacs-mod 'emacs-minimal)))
 
 (define* (lower name
                 #:key source inputs native-inputs outputs system target