CLJS-1580: Self-host: goog.provide offsets source-maps

When goog.provide is emitted as a result of processing :ns :op, this
modification to the JavaScript offsets the lines in that file by one,
thus messing up source mapping lines, if enabled. Instead of simply
using str to generate the line, use comp/emitln, which internally does
the proper accounting with respect to source maps.

Author: mfikes

src/main/cljs/cljs/js.cljs

@@ -732,7 +732,7 @@
                       (if (= :ns (:op ast))
                         (do
                           (.append sb
-                            (str "goog.provide(\"" (munge (:name ast)) "\");\n"))
+                            (with-out-str (comp/emitln (str "goog.provide(\"" (munge (:name ast)) "\");"))))
                           (ns-side-effects true bound-vars aenv ast opts
                             (fn [res]
                               (if (:error res)