start builtin.rb without RUBYOPT environment variable to get more accurate results
diff --git a/plugins/org.eclipse.dltk.ruby.launching/src/org/eclipse/dltk/ruby/internal/launching/RubyGenericInstall.java b/plugins/org.eclipse.dltk.ruby.launching/src/org/eclipse/dltk/ruby/internal/launching/RubyGenericInstall.java
index d10ef36..a67a7e5 100644
--- a/plugins/org.eclipse.dltk.ruby.launching/src/org/eclipse/dltk/ruby/internal/launching/RubyGenericInstall.java
+++ b/plugins/org.eclipse.dltk.ruby.launching/src/org/eclipse/dltk/ruby/internal/launching/RubyGenericInstall.java
@@ -51,6 +51,7 @@
 			InterpreterConfig config = ScriptLaunchUtil
 					.createInterpreterConfig(exeEnv, builderFile, builderFile
 							.getParent());
+			config.removeEnvVar("RUBYOPT"); //$NON-NLS-1$
 			// config.addInterpreterArg("-KU"); //$NON-NLS-1$
 			final Process process = ScriptLaunchUtil.runScriptWithInterpreter(
 					exeEnv, RubyGenericInstall.this.getInstallLocation()