Can external stylesheet be included in spec build output?

The spec HTML references an external stylesheet:

Is there a way to make this stylesheet included in the build output? (other than downloading it manually and patching the html to point to local file instead)

What I'm really asking is for git clone --branch gh-pages to be self-contained. It's not a big deal, the documentation is still perfectly readable off-line from such clone, only some code examples lack syntax highlighting.