Get cloudflare to install graphviz.

build.sh

@@ -12,12 +12,14 @@ set -euo pipefail
 # We only support macOS (the x86 binaries work OK on Apple Silicon), or x86-64 Linux
 if [ $(uname) == "Darwin" ]; then
     ./mdbook --version || curl -sSL https://github.com/rust-lang/mdBook/releases/download/v0.4.40/mdbook-v0.4.40-x86_64-apple-darwin.tar.gz | tar -xvzf -
+    dot --version || brew install graphviz
     mdbook-graphviz --version || cargo install mdbook-graphviz
     ./mdslides --version || ( curl -sSL https://github.com/ferrous-systems/mdslides/releases/download/v0.4.0/mdslides-x86_64-apple-darwin.tar.xz | tar -xvJf - \
         && mv ./mdslides-*/mdslides . \
         && rm -rf ./mdslides-*/ )
 else
     ./mdbook --version || curl -sSL https://github.com/rust-lang/mdBook/releases/download/v0.4.40/mdbook-v0.4.40-x86_64-unknown-linux-gnu.tar.gz | tar -xvzf -
+    dot --version || ( apt-get update -y && apt-get install -y graphviz )
     ./mdbook-graphviz --version || ( curl -sSL https://github.com/dylanowen/mdbook-graphviz/releases/download/v0.2.1/mdbook-graphviz_v0.2.1_x86_64-unknown-linux-musl.zip -o mdbook-graphviz.zip \
         && unzip mdbook-graphviz.zip \
         && rm mdbook-graphviz.zip \