[ci] Use more optimizer threads (#138320)

.buildkite/scripts/build_kibana_plugins.sh

@@ -3,4 +3,5 @@
 set -euo pipefail
 
 echo "--- Build Platform Plugins"
-node scripts/build_kibana_platform_plugins --examples --test-plugins
+THREADS=$(grep -c ^processor /proc/cpuinfo)
+node scripts/build_kibana_platform_plugins --examples --test-plugins --workers "$THREADS" --no-inspect-workers --no-progress

src/dev/build/tasks/build_kibana_platform_plugins.ts

@@ -31,6 +31,7 @@ export const BuildKibanaPlatformPlugins: Task = {
       watch: false,
       dist: true,
       includeCoreBundle: true,
+      inspectWorkers: false,
       limitsPath: Path.resolve(REPO_ROOT, 'packages/kbn-optimizer/limits.yml'),
     });