RJIT: Print an error message first

Creating a backtrace can crash if RJIT is triggered by branch_stub_hit.
In that case, it's useful to at least print the error message.

lib/ruby_vm/rjit/compiler.rb

@@ -67,7 +67,8 @@ module RubyVM::RJIT
       compile_block(asm, jit:, pc:)
       iseq.body.jit_entry = @cb.write(asm)
     rescue Exception => e
-      $stderr.puts e.full_message
+      $stderr.puts "#{e.class}: #{e.message}"
+      $stderr.puts e.backtrace
       exit 1
     end