flush output when writing .go files

* module/system/base/compile.scm (call-with-output-file/atomic): Close
  the port we are writing to before renaming it, so that we flush output.
  Might fix some 0-length write errors that Jao was seeing.

module/system/base/compile.scm

@@ -78,6 +78,7 @@
        (with-throw-handler #t
          (lambda ()
            (proc tmp)
+           (close-port tmp)
            (rename-file template filename))
          (lambda args
            (delete-file template)))))))