tools: ignore build folder when checking links

We checkout build as a subdirectory as part of CI and
if you run `make test` instead of `make test-ci` you get
loads of errors about markdown link breaks. Ignore this
directory as we don't need to examine another repo

PR-URL: #35315
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

tools/doc/checkLinks.js

@@ -27,6 +27,7 @@ function findMarkdownFilesRecursively(dirPath) {
     if (
       entry.isDirectory() &&
       entry.name !== 'api' &&
+      entry.name !== 'build' &&
       entry.name !== 'changelogs' &&
       entry.name !== 'deps' &&
       entry.name !== 'fixtures' &&