This is necessary to be able to use arbitrary zig allocators as the cmark allocator. I'm not sure if this patch is worth trying to upstream.
subrepo: subdir: "deps/cmark" merged: "5ba25ff" upstream: origin: "https://github.com/commonmark/cmark.git" branch: "0.30.3" commit: "5ba25ff" git-subrepo: version: "0.4.6" commit: "d4444b563"