Added example for cross-compiling for Sega Dreamcast (sh-elf).
Thanks to for demonstrating mruby usage on Sega Dreamcast at RubyConf AU 2020!
See more here:
ADD
examples/targets/build_config_dreamcast_shelf.rb
+MRuby::Build.new do |conf|
+
+ # 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 'default'
+
+end
+
+# Cross Compiling configuration for Sega Dreamcast
+# This requires KallistiOS to be installed
+# https://dreamcast.wiki
+#
+MRuby::CrossBuild.new("dreamcast") do |conf|
+ toolchain :gcc
+
+ # Supporting DreamSDK (if necessarys)
+ DREAMSDK_HOME = ENV["DREAMSDK_HOME"]
+ MSYS_ROOT = !(DREAMSDK_HOME.nil? || DREAMSDK_HOME.empty?) ? "#{DREAMSDK_HOME}/msys/1.0" : ""
+
+ # For all host systems
+ DREAMCAST_PATH = "#{MSYS_ROOT}/opt/toolchains/dc"
+ KOS_PATH = "#{DREAMCAST_PATH}/kos"
+ BIN_PATH = "#{DREAMCAST_PATH}/sh-elf/bin"
+
+ 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 = "%{flags} -o %{outfile} -c %{infile}"
+ cc.defines << %w(_arch_dreamcast)
+ cc.defines << %w(_arch_sub_pristine)
+ end
+
+ 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
+
+ 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
+
+ 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
+ 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

Added example for cross-compiling for Sega Dreamcast (sh-elf).
Thanks to @yujiyokoo for demonstrating mruby usage on Sega Dreamcast at RubyConf AU 2020!
See more here: https://youtu.be/ni-1x5Esa_o