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
```
The `mrb` command executes only precompiled RiteBinary (.mrb) files
without depending on mruby-compiler. This enables smaller binaries
for embedded deployments where scripts are precompiled on a
development machine.
Co-authored-by: Claude <noreply@anthropic.com>