Don't recompile mdbook from scratch

Author: Toby222

.github/workflows/mdbook.yml

@@ -33,11 +33,13 @@ jobs:
       MDBOOK_VERSION: ^0.5
     steps:
     - uses: actions/checkout@v4
-    - name: Install mdBook
+    - name: Install latest mdbook
       run: |
-        curl --proto '=https' --tlsv1.2 https://sh.rustup.rs -sSf -y | sh
-        rustup update
-        cargo install --version ${MDBOOK_VERSION} mdbook
+        tag=$(curl 'https://api.github.com/repos/rust-lang/mdbook/releases/latest' | jq -r '.tag_name')
+        url="https://github.com/rust-lang/mdbook/releases/download/${tag}/mdbook-${tag}-x86_64-unknown-linux-gnu.tar.gz"
+        mkdir mdbook
+        curl -sSL $url | tar -xz --directory=./mdbook
+        echo `pwd`/mdbook >> $GITHUB_PATH
     - name: Setup Pages
       id: pages
       uses: actions/configure-pages@v5