Use the existing mechanism to adapt the timeout in MRI tests's EnvUtil

Author: eregon

test/mri/tests/lib/envutil.rb

@@ -67,6 +67,9 @@ def capture_global_values
     end
   end
 
+  # TruffleRuby: startup can take longer, especially on highly loaded CI machines
+  self.subprocess_timeout_scale = 2
+
   def apply_timeout_scale(t)
     if scale = EnvUtil.subprocess_timeout_scale
       t * scale
@@ -77,7 +80,7 @@ def apply_timeout_scale(t)
   module_function :apply_timeout_scale
 
   def invoke_ruby(args, stdin_data = "", capture_stdout = false, capture_stderr = false,
-                  encoding: nil, timeout: 20, reprieve: 1, timeout_error: Timeout::Error,
+                  encoding: nil, timeout: 10, reprieve: 1, timeout_error: Timeout::Error,
                   stdout_filter: nil, stderr_filter: nil,
                   signal: :TERM,
                   rubybin: EnvUtil.rubybin, precommand: nil,