Compile javascript

This is needed for the jsbunding-rails support (Propshaft build) now that 1.1.0 is out. This change rails/jsbundling-rails#128 means the build is no longer triggered on db:test:prepare

Author: jcoyne

tasks/blacklight.rake

@@ -44,6 +44,10 @@ end
 # rubocop:disable Rails/RakeEnvironment
 desc "Run test suite"
 task :ci do
+  within_test_app do
+    # Precompiles the javascript
+    system "bin/rake test:prepare"
+  end
   with_solr do
     Rake::Task['blacklight:internal:seed'].invoke
     Rake::Task['blacklight:coverage'].invoke