Previously, `libmruby.a` was created even if only `mruby-bin-mrbc` or`
mruby-compiler` was specified for gem, but by specifying `disable_libmruby`,
the creation of `libmruby.a` can be suppressed.
### Note
The https://github.com/mruby/mruby/pull/5084#issuecomment-723521971
incompatibility seems to be difficult for users to avoid, so the original
behavior has been restored. Therefore, if we need `mrbc` other than the
`host` build, we need to explicitly specify `mruby-bin-mrbc` gem.
Due to the above changes, `build_config/boxing.rb` etc. will not work, but I
have added` mruby-bin-mrbc` to `default.gembox` to fix it. I don't think
this change is a big deal because originally `mruby-compiler` was included.
Module#include and Module#prepend now affect classes and modules
that have already included or prepended the receiver, mirroring the
behavior if the arguments were included in the receiver before
the other modules and classes included or prepended the receiver.
```ruby
class C; end
module M1; end
module M2; end
C.include M1
M1.include M2
p C.ancestors #=> [C, M1, M2, Object, Kernel, BasicObject]
```
Currently, adding gems to build configuration and rebuilding does not
regenerate `presym`, which can lead to build errors.
Therefore in this case we need to remove the `presym` file and then rebuild
mruby, but when the` presym` file is regenerated we will need to recompile
most of the files, so it seems useful to have the `presym` file deleted by
`rake clean`.
Due to the above changes, it may not work with the existing build
configurations in cross-compilation (even if we can build without presym),
therefore revert it once (ref https://github.com/mruby/mruby/pull/5202#issuecomment-735412643). Sorry for the lack of consideration.
Currently, the size of writing in heap by write_irep_record() is
bigger than The size that is calculated by get_irep_record_size.
Therefore, irep is dumped over the size of allocating memory when we
execute dump_irep().
Previously, presym files were always created in `build/{presym,presym.inc}`.
However, this constraint is inconvenient because it is common to use
multiple build configurations and build targets in a single mruby tree.
Therefore, change to create presym file for each build target.
Jump target address is `operand (16bit)` + `address of next instruction`.
In addition, `ilen` was made `uint32_t` so that `iseq` length limitation
of 65536 is removed. Only jump target address should be within signed
16bit (-32768 .. 32767).
Yukihiro "Matz" Matsumoto