ci(llvm-matrix): filter uses Node.js 20

.github/llvm-matrix.js

@@ -1,3 +1,8 @@
+// Description: This script reads the matrix.json file and filters
+// out entries that already have an existing llvm-archive-filename on the server.
+// This creates a filtered matrix used to upload new archives to the server, but
+// only the ones that don't already exist.
+
 const fs = require('fs');
 const core = require('@actions/core');
 const { exec } = require('child_process');

.github/package.json

@@ -0,0 +1,5 @@
+{
+  "dependencies": {
+    "@actions/core": "^1.11.0"
+  }
+}

.github/workflows/ci.yml

@@ -72,11 +72,19 @@ jobs:
             mrdocs-package-generators: {{#if (ieq os 'windows') }}7Z ZIP WIX{{else}}TGZ TXZ{{/if}}
           output-file: matrix.json
 
+      # Set up the version as expected by the LLVM matrix script and @actions/core
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+
       - name: Generate LLVM Test Matrix
         id: llvm-matrix
         run: |
           set -x
-          npm install @actions/core
+          cd .github
+          npm ci
+          cd ..
           node .github/llvm-matrix.js
 
   build: