ci: install build deps from AL2023 S3 repo for VPC runners

The CodeBuild runners have no public internet egress, so the default
cdn.amazonlinux.com mirrorlist is unreachable. Point dnf at the regional
al2023-repos S3 bucket (reachable via the VPC's S3 gateway endpoint) and
disable the image's unreachable third-party repos.

Author: maxday

.github/workflows/release.yml

@@ -41,7 +41,22 @@ jobs:
 
     steps:
       - name: Install prerequisites
-        run: dnf install -y tar gzip git cmake ninja-build gcc-c++ openssl-devel libcurl-devel
+        run: |
+          # The CodeBuild runners live in a VPC with no public egress, so the
+          # default cdn.amazonlinux.com mirrorlist (and the image's Corretto /
+          # gh-cli / mono repos) can't be reached. Point dnf at the regional
+          # AL2023 repo bucket, which is reachable via the VPC's S3 gateway
+          # endpoint, and disable everything else.
+          cat > /etc/yum.repos.d/al2023-s3.repo <<'EOF'
+          [al2023-s3]
+          name=AL2023 core via S3 gateway endpoint
+          mirrorlist=https://al2023-repos-eu-west-1.s3.dualstack.eu-west-1.amazonaws.com/core/mirrors/$releasever/$basearch/mirror.list
+          gpgcheck=1
+          gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-amazon-linux-2023
+          enabled=1
+          EOF
+          dnf --disablerepo='*' --enablerepo='al2023-s3' install -y \
+            tar gzip git cmake ninja-build gcc-c++ openssl-devel libcurl-devel
 
       - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with: