Existence of priv directory breaks Distillery releases

Hello! I have been trying to use fast_html in a Distillery release and I believe I've found an issue caused by the existence of the priv directory. The elixir_make docs mention that the source code must not have a priv dir https://github.com/elixir-lang/elixir_make/blob/master/lib/mix/tasks/compile.make.ex#L94

I've got a working fork over at github, but the gist (pun intended) of the fix is:

• Remove the priv directory
• mkdir priv in Makefile, specifically the priv/fasthtml_worker target. After compiling lexbor but before compiling fasthtml_worker, simply mkdir priv

That should be enough to fix it. I've confirmed that my fork builds correctly and the compiled binary is reachable.