Drop binary gems support

Rakefile

@@ -2,9 +2,6 @@ require "bundler/gem_tasks"
 require "rake/testtask"
 
 name = "etc"
-specfile = name.tr("/", "-")+".gemspec"
-
-VERSIONS = %w[2.4.0 2.5.0 2.6.0]
 
 headers = ["ext/etc/constdefs.h"]
 task compile: headers
@@ -14,29 +11,11 @@ file "ext/etc/constdefs.h" => "ext/etc/mkconstants.rb" do |t|
 end
 
 Rake::TestTask.new(:test) do |t|
-  t.libs << "test" << "test/lib"
+  t.libs << "test"
   t.libs << "lib"
   t.test_files = FileList["test/**/test_*.rb"]
 end
 
 require 'rake/extensiontask'
-spec = eval(File.read(specfile), nil, specfile)
-spec.files.delete_if {|n| %r'\Aext/' =~ n}
-spec.extensions.clear
-spec.require_paths.insert(0, *%w[stub])
-Rake::ExtensionTask.new(name, spec) do |ext|
-  ext.cross_compile = true
-  ext.cross_platform = %w[x86-mingw32 x64-mingw32]
-  ext.cross_compiling do |s|
-    s.files.concat VERSIONS.map {|v| "lib/#{v[/\A\d+\.\d+/]}/#{name}.so"}
-  end
-end
-
-desc "Compile binaries for mingw platform using rake-compiler-dock"
-task 'build:mingw' do
-  require 'rake_compiler_dock'
-  RakeCompilerDock.sh "bundle && rake cross native gem RUBY_CC_VERSION=#{VERSIONS.join(':')}"
-end
-task 'build:mingw' => headers
-
-task :default => [:compile, :test]
+Rake::ExtensionTask.new(name)
+task :default => :test

etc.gemspec

@@ -29,7 +29,6 @@ Gem::Specification.new do |spec|
     ext/etc/etc.c
     ext/etc/extconf.rb
     ext/etc/mkconstants.rb
-    stub/etc.rb
     test/etc/test_etc.rb
   ]
   spec.bindir        = "exe"