Disable test on 1.8.7, since workaround is to allow blocking on that version

spec/process_shared/semaphore_spec.rb

@@ -158,6 +158,7 @@ module ProcessShared
         end
       end
 
+      unless RUBY_VERSION == '1.8.7'
         it 'allows other threads in a process to continue while waiting' do
           start = Time.now.to_f
           sem = Semaphore.new
@@ -190,4 +191,5 @@ module ProcessShared
         end
       end
     end
+  end
 end