Test that Truffle options are correctly applied

(cherry picked from commit e90f32c)

Author: eregon

spec/truffle/launcher_spec.rb

@@ -287,7 +287,7 @@ def should_print_full_java_command(options, env: {})
         "#{prefix}Dgraal.TraceTruffleCompilation=true",
         "#{prefix}Dgraal.TruffleBackgroundCompilation=false",
       ].join(" ")
-      out = ruby_exe("2000.times {}", options: options)
+      out = ruby_exe("2000.times {}", options: options, args: "2>&1")
       out.should include("[truffle] opt done")
     end
   end