Add TODO(#89)

third_party/build_third_party.sh

@@ -1,6 +1,6 @@
 #!/bin/sh
 
-# TODO: Integrate ./build_third_party.sh into the main build process
+# TODO(#89): Integrate ./build_third_party.sh into the main build process
 FFMPEG_VERSION=4.3
 GIFLIB_VERSION=5.2.1