Reuse xmllint script in check-build.yml

.github/workflows/check-build.yml

@@ -35,9 +35,7 @@ jobs:
     - name: XML validation
       run: |
         sudo apt-get install -y libxml2-utils
-        for i in xml/issue*.xml ; do
-          xmllint --noout --nowarning --dtdvalid xml/lwg-issue.dtd $i
-        done
+        bin/lint.sh
 
     - name: Generate HTML lists
       run: make lists