Include sky_snapshot in binary distribution

sky/dist/BUILD.gn

@@ -44,6 +44,15 @@ copy("sky_shell") {
     ]
   }
 
+  sky_snapshot_dir =
+      get_label_info("//sky/tools/sky_snapshot($host_toolchain)", "root_out_dir")
+
+  sources += [ "$sky_snapshot_dir/sky_snapshot" ]
+
+  deps += [
+    "//sky/tools/sky_snapshot($host_toolchain)",
+  ]
+
   outputs = [ "$root_dist_dir/shell/{{source_file_part}}" ]
 }