ci: clean-up scripts.

- use /bin/sh shebang for check-summary.  Works just fine and avoids
  pulling in bash for the CI run
- don't fetch upstream repository, not necessary
- don't specify ubuntu version
- use mini-x86_64-musl image to speed up container setup (mini-bb is
  having trouble with certs)

Author: ericonr

.github/workflows/ci.yaml

@@ -4,9 +4,9 @@ on: pull_request
 jobs:
   only:
     name: Check formatting and links
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     container:
-      image: ghcr.io/void-linux/void-linux:latest-full-x86_64-musl
+      image: ghcr.io/void-linux/void-linux:latest-mini-x86_64-musl
     steps:
       - name: Prepare container
         run: |

res/ci/check-summary.sh

@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#!/bin/sh
 
 cd src/ || exit 2
 

res/ci/format.sh

@@ -1,8 +1,5 @@
 #!/bin/sh
 
-# Fetch upstream
-git fetch git://github.com/void-linux/void-docs.git master
-
 echo "Checking links"
 RUST_LOG=linkcheck=debug mdbook-linkcheck -s
 LINKCHECK=$?