Revert `MRUBY_TARGET` mechanism; ref #5096

* 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).

1 files changed, 26 insertions, 0 deletions

diff --git a/build_config/host-debug.rb b/build_config/host-debug.rb
new file mode 100644
index 000000000..ad4106065
--- /dev/null
+++ b/build_config/host-debug.rb
@@ -0,0 +1,26 @@
+MRuby::Build.new('host') do |conf|
+  # load specific toolchain settings
+
+  # Gets set by the VS command prompts.
+  if ENV['VisualStudioVersion'] || ENV['VSINSTALLDIR']
+    toolchain :visualcpp
+  else
+    toolchain :gcc
+  end
+
+  enable_debug
+
+  # include the default GEMs
+  conf.gembox 'full-core'
+
+  # C compiler settings
+  conf.cc.defines = %w(MRB_ENABLE_DEBUG_HOOK MRB_NO_BOXING)
+
+  # Generate mruby debugger command (require mruby-eval)
+  conf.gem :core => "mruby-bin-debugger"
+
+  # test
+  enable_test
+  # bintest
+  enable_bintest
+end