build: Define compatible jruby/jruby-rack more accurately; allow ostruct patches

Author: chadlwilson

warbler.gemspec

@@ -30,10 +30,10 @@ bundle up all of your application files for deployment to a Java environment.}
 
   gem.add_runtime_dependency 'rake', ['~> 13.0', '>= 13.0.3']
   gem.add_runtime_dependency 'rexml', '~> 3.0'
-  gem.add_runtime_dependency 'jruby-jars', ['>= 9.0.0']
-  gem.add_runtime_dependency 'jruby-rack', ['>= 1.1.1', '< 1.3']
+  gem.add_runtime_dependency 'jruby-jars', ['>= 9.4', '< 10.1']
+  gem.add_runtime_dependency 'jruby-rack', ['>= 1.2.3', '< 1.3']
   gem.add_runtime_dependency 'rubyzip', '>= 3.0.0'
-  gem.add_runtime_dependency 'ostruct', '0.6.2'
+  gem.add_runtime_dependency 'ostruct', '~> 0.6.2'
   gem.add_development_dependency 'jbundler', '0.9.5'
   gem.add_development_dependency 'rspec', '~> 3.0'
 end