Add :truffle_bug as a tag on some specs that don't work on JRuby+Truffle.

Author: chrisseaton

spec/concurrent/channel/tick_spec.rb

@@ -26,7 +26,7 @@ class Channel
         expect(subject.utc.to_f).to eq subject.epoch
       end
 
-      specify do
+      specify '#to_s formats as a time', :truffle_bug => true do
         expect(subject.to_s).to match /\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}\.\d{6} \+\d{4} UTC/
       end
 

spec/concurrent/executor/thread_pool_executor_shared.rb

@@ -100,7 +100,7 @@
       expect(subject.max_queue).to eq expected_max
     end
 
-    it 'returns the set value when running' do
+    it 'returns the set value when running', :truffle_bug => true do # only actually fails for RubyThreadPoolExecutor
       trigger = Concurrent::Event.new
       5.times{ subject.post{ trigger.wait } }
       expect(subject.max_queue).to eq expected_max
@@ -115,7 +115,7 @@
     end
   end
 
-  context '#queue_length' do
+  context '#queue_length', :truffle_bug => true do # only actually fails for RubyThreadPoolExecutor
 
     let!(:expected_max){ 10 }
     subject do