dearblue a98c6b62ea Don't use #puts in bintest for "mruby-bin-mrb" ...

Since `Kernel#puts` is undefined in unit tests, using `Kernel#print` is required.
Previously, for example, running `rake test` with the following build configuration caused the tests to fail.

```ruby
MRuby::Build.new do
  toolchain
  enable_debug
  enable_test
  enable_bintest
  gem core: "mruby-bin-mrb"
end
```

2026-05-02 20:52:00 +09:00

..

mrb.rb

Don't use #puts in bintest for "mruby-bin-mrb"

2026-05-02 20:52:00 +09:00