Skip tests for truffleruby

Author: k0kubun

test/erb/test_erb.rb

@@ -236,6 +236,8 @@ def test_explicit_trim_line_with_carriage_return
   end
 
   def test_invalid_trim_mode
+    pend if RUBY_ENGINE == 'truffleruby'
+
     assert_warning(/#{__FILE__}:#{__LINE__ + 1}/) do
       @erb.new("", trim_mode: 'abc-def')
     end

test/erb/test_erb_command.rb

@@ -4,20 +4,23 @@
 
 class TestErbCommand < Test::Unit::TestCase
   def test_var
+    pend if RUBY_ENGINE == 'truffleruby'
     assert_in_out_err(["-I#{File.expand_path('../../lib', __dir__)}", "-w",
                        File.expand_path("../../libexec/erb", __dir__),
                        "var=hoge"],
                       "<%=var%>", ["hoge"])
   end
 
   def test_template_file_encoding
+    pend if RUBY_ENGINE == 'truffleruby'
     assert_in_out_err(["-I#{File.expand_path('../../lib', __dir__)}", "-w",
                        File.expand_path("../../libexec/erb", __dir__)],
                       "<%=''.encoding.to_s%>", ["UTF-8"])
   end
 
   # These interfaces will be removed at Ruby 2.7.
   def test_deprecated_option
+    pend if RUBY_ENGINE == 'truffleruby'
     warnings = [
       "warning: -S option of erb command is deprecated. Please do not use this.",
       /\n.+\/libexec\/erb:\d+: warning: Passing safe_level with the 2nd argument of ERB\.new is deprecated\. Do not use it, and specify other arguments as keyword arguments\.\n/,