Skip test_inspect_under_gc_compact_stress w/ RJIT too

test/ruby/test_symbol.rb

@@ -121,6 +121,7 @@ class TestSymbol < Test::Unit::TestCase
   def test_inspect_under_gc_compact_stress
     omit "compaction doesn't work well on s390x" if RUBY_PLATFORM =~ /s390x/ # https://github.com/ruby/ruby/pull/5077
     omit "very flaky on many platforms, more so with YJIT enabled" if defined?(RubyVM::YJIT) && RubyVM::YJIT.enabled?
+    omit "very flaky on many platforms, more so with RJIT enabled" if defined?(RubyVM::RJIT) && RubyVM::RJIT.enabled?
     EnvUtil.under_gc_compact_stress do
       assert_inspect_evaled(':testing')
     end