deploy: Log calculated needed space

To aid debugging issues like coreos/fedora-coreos-tracker#1637

If we're hitting this path where we think we have enough space,
let's log what we calculated here to aid in diagnosing why we
may later fail with ENOSPC.

src/libostree/ostree-sysroot-deploy.c

@@ -2667,7 +2667,11 @@ auto_early_prune_old_deployments (OstreeSysroot *self, GPtrArray *new_deployment
     /* does the bootfs have enough free space for temporarily holding both the new
      * and old bootdirs? */
     if (bootfs_has_space)
-      return TRUE; /* nothing to do! */
+      {
+        g_autofree char *net_new_formatted = g_format_size (net_new_bootcsum_dirs_total_size);
+        g_print ("bootfs is sufficient for calculated new size: %s\n", net_new_formatted);
+        return TRUE; /* nothing to do! */
+      }
   }
 
   /* OK, we would fail if we tried to write the new bootdirs. Is it salvageable?