Port report-emacs-bug to deterministic builds

* lisp/mail/emacsbug.el (report-emacs-bug): Future-proof the
recent "built on" change to deterministic builds where
emacs-build-system will be nil.  See:
http://lists.gnu.org/archive/html/emacs-devel/2015-12/msg01369.html

1 files changed, 5 insertions, 1 deletions

diff --git a/lisp/mail/emacsbug.el b/lisp/mail/emacsbug.el
index ae0e711d814..ef5e86a6c8b 100644
--- a/lisp/mail/emacsbug.el
+++ b/lisp/mail/emacsbug.el
@@ -242,7 +242,11 @@ usually do not have translators for other languages.\n\n")))
     (let ((txt (delete-and-extract-region (1+ user-point) (point))))
       (insert (propertize "\n" 'display txt)))
 
-    (insert "\n\nIn " (emacs-version) " built on " emacs-build-system "\n")
+    (insert "\n\nIn " (emacs-version))
+    (if emacs-build-system
+        (insert " built on " emacs-build-system))
+    (insert "\n")
+
     (if (stringp emacs-repository-version)
         (insert "Repository revision: " emacs-repository-version "\n"))
     (if (fboundp 'x-server-vendor)