[ruby/cgi] Add TruffleRuby support and add it in CI

https://github.com/ruby/cgi/commit/1240fec9c9

ext/cgi/escape/extconf.rb

@@ -1,3 +1,7 @@
 require 'mkmf'
 
-create_makefile 'cgi/escape'
+if RUBY_ENGINE == 'truffleruby'
+  File.write("Makefile", dummy_makefile($srcdir).join(""))
+else
+  create_makefile 'cgi/escape'
+end

lib/cgi/util.rb

@@ -90,9 +90,12 @@ module CGI::Util
     end
   end
 
-  begin
-    require 'cgi/escape'
-  rescue LoadError
+  # TruffleRuby runs the pure-Ruby variant faster, do not use the C extension there
+  unless RUBY_ENGINE == 'truffleruby'
+    begin
+      require 'cgi/escape'
+    rescue LoadError
+    end
   end
 
   # Unescape a string that has been HTML-escaped

test/cgi/test_cgi_util.rb

@@ -262,7 +262,7 @@ class CGIUtilPureRubyTest < Test::Unit::TestCase
       remove_method :escapeHTML
       alias _unescapeHTML unescapeHTML
       remove_method :unescapeHTML
-    end
+    end if defined?(CGI::Escape)
   end
 
   def teardown
@@ -271,7 +271,7 @@ class CGIUtilPureRubyTest < Test::Unit::TestCase
       remove_method :_escapeHTML
       alias unescapeHTML _unescapeHTML
       remove_method :_unescapeHTML
-    end
+    end if defined?(CGI::Escape)
   end
 
   def test_cgi_escapeHTML_with_invalid_byte_sequence