use umask when making permissions on .go files

* module/system/base/compile.scm (call-with-output-file/atomic): Temp
  files get created 0600. After we're done writing, chmod them to
  something in line with the user's umask.

module/system/base/compile.scm

@@ -78,6 +78,7 @@
        (with-throw-handler #t
          (lambda ()
            (proc tmp)
+           (chmod tmp (logand #o0666 (lognot (umask))))
            (close-port tmp)
            (rename-file template filename))
          (lambda args