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, 94 insertions, 0 deletions

diff --git a/build_config/dreamcast_shelf.rb b/build_config/dreamcast_shelf.rb
new file mode 100644
index 000000000..3ae53184d
--- /dev/null
+++ b/build_config/dreamcast_shelf.rb
@@ -0,0 +1,94 @@
+# Cross Compiling configuration for the Sega Dreamcast
+# This configuration requires KallistiOS (KOS)
+# https://dreamcast.wiki
+#
+# Tested on GNU/Linux, MinGW-w64/MSYS2, Cygwin, macOS and MinGW/MSYS (see below)
+#
+MRuby::CrossBuild.new("dreamcast") do |conf|
+  toolchain :gcc
+
+  # Support for DreamSDK (based on MinGW/MSYS)
+  # To compile mruby with DreamSDK, RubyInstaller for Windows should be installed
+  DREAMSDK_HOME = ENV["DREAMSDK_HOME"]
+  MSYS_ROOT = !(DREAMSDK_HOME.nil? || DREAMSDK_HOME.empty?) ? "#{DREAMSDK_HOME}/msys/1.0" : ""
+ 
+  # Setting paths
+  DREAMCAST_PATH = "#{MSYS_ROOT}/opt/toolchains/dc"
+  KOS_PATH = "#{DREAMCAST_PATH}/kos"
+  BIN_PATH = "#{DREAMCAST_PATH}/sh-elf/bin"
+
+  # C compiler
+  # Flags were extracted from KallistiOS environment files
+  conf.cc do |cc|
+    cc.command = "#{BIN_PATH}/sh-elf-gcc"	
+    cc.include_paths << ["#{KOS_PATH}/include", "#{KOS_PATH}/kernel/arch/dreamcast/include", "#{KOS_PATH}/addons/include", "#{KOS_PATH}/../kos-ports/include"]
+    cc.flags << ["-O2", "-fomit-frame-pointer", "-ml", "-m4-single-only", "-ffunction-sections", "-fdata-sections", "-Wall", "-g", "-fno-builtin", "-ml", "-m4-single-only", "-Wl,-Ttext=0x8c010000", "-Wl,--gc-sections", "-T#{KOS_PATH}/utils/ldscripts/shlelf.xc", "-nodefaultlibs"]
+    cc.compile_options = %Q[%{flags} -o "%{outfile}" -c "%{infile}"]
+    cc.defines << %w(_arch_dreamcast)
+    cc.defines << %w(_arch_sub_pristine)
+  end
+
+  # C++ compiler
+  conf.cxx do |cxx|
+    cxx.command = conf.cc.command.dup
+    cxx.include_paths = conf.cc.include_paths.dup
+    cxx.flags = conf.cc.flags.dup
+    cxx.flags << %w(-fno-rtti -fno-exceptions)
+    cxx.defines = conf.cc.defines.dup
+    cxx.compile_options = conf.cc.compile_options.dup
+  end
+ 
+  # Linker
+  # There is an issue when making the mruby library with KallistiOS:
+  # 'newlib_kill.o' and 'newlib_getpid.o' aren't found so they are explicitly 
+  # specified here at least for now.
+  conf.linker do |linker|
+    linker.command="#{BIN_PATH}/sh-elf-gcc"
+    linker.flags << ["#{MSYS_ROOT}/opt/toolchains/dc/kos/kernel/build/newlib_kill.o", "#{MSYS_ROOT}/opt/toolchains/dc/kos/kernel/build/newlib_getpid.o", "-Wl,--start-group -lkallisti -lc -lgcc -Wl,--end-group"]
+    linker.library_paths << ["#{KOS_PATH}/lib/dreamcast", "#{KOS_PATH}/addons/lib/dreamcast", "#{KOS_PATH}/../kos-ports/lib"]
+  end  
+
+  # Archiver
+  conf.archiver do |archiver|
+    archiver.command = "#{BIN_PATH}/sh-elf-ar"
+    archiver.archive_options = 'rcs "%{outfile}" %{objs}'
+  end
+
+  # No executables
+  conf.bins = []
+
+  # Do not build executable test
+  conf.build_mrbtest_lib_only
+
+  # Disable C++ exception
+  conf.disable_cxx_exception
+  
+  # Gems from core
+  # removing mruby-io
+  conf.gem :core => "mruby-metaprog"
+  conf.gem :core => "mruby-pack"
+  conf.gem :core => "mruby-sprintf"
+  conf.gem :core => "mruby-print"
+  conf.gem :core => "mruby-math"
+  conf.gem :core => "mruby-time"
+  conf.gem :core => "mruby-struct"
+  conf.gem :core => "mruby-compar-ext"
+  conf.gem :core => "mruby-enum-ext"
+  conf.gem :core => "mruby-string-ext"
+  conf.gem :core => "mruby-numeric-ext"
+  conf.gem :core => "mruby-array-ext"
+  conf.gem :core => "mruby-hash-ext"
+  conf.gem :core => "mruby-range-ext"
+  conf.gem :core => "mruby-proc-ext"
+  conf.gem :core => "mruby-symbol-ext"
+  conf.gem :core => "mruby-random"
+  conf.gem :core => "mruby-object-ext"
+  conf.gem :core => "mruby-objectspace"
+  conf.gem :core => "mruby-fiber"
+  conf.gem :core => "mruby-enumerator"
+  conf.gem :core => "mruby-enum-lazy"
+  conf.gem :core => "mruby-toplevel-ext"
+  conf.gem :core => "mruby-kernel-ext"
+  conf.gem :core => "mruby-class-ext"
+  conf.gem :core => "mruby-compiler"
+end