* In explanation of mruby, the expression `build_config.rb` is frequently
used including official documents, so I think that it will not make sense
if the file is no longer used.
* The `MRUBY_TARGET` mechanism seems to have little improvement, so I don't
think it should be changed to avoid unnecessary confusion.
* `MRUBY_TARGET` and `MRuby.targets` represent somewhat different things,
so using the same term "target" is a bit confusing.
The mechanism that can be written short when using a file under
`build_config` (renamed from `target`) directory remains
(`build_config/${MRUBY_CONFIG}.rb` is used if the path specified
in `MRUBY_CONFIG` doesn't exist).
You have to specify `TARGET` to specify a configuration, e.g.
```
rake TARGET=host-debug all test
```
When you port `mruby` to a new configuration:
1. copy an existing configuration under `target` directory
2. modify the new configuration file
3. build using the new configuration
4. send PR if you please
- Defer YAML library and lock file loading until needed.
- Don't write empty parts into lock file.
- Extract code to read/write lock file to `MRuby::Lockfile`.
- `MRuby::Lockfile.disable` disables the use of lock file.
KOBAYASHI Shuji