Binary gem cross-compilation via rake-compiler-dock

Simply have Docker installed and run this to compile binary gems:

    bundle exec rake gem:native

Rakefile

@@ -1,16 +1,22 @@
-begin
-  require 'bundler/gem_tasks'
-rescue LoadError
-  puts 'Cannot load bundler/gem_tasks'
-end
+require 'bundler/gem_tasks'
 
 task default: :test
 
 require 'rake/extensiontask'
-Rake::ExtensionTask.new do |ext|
+gem_spec = Gem::Specification.load("sassc.gemspec")
+Rake::ExtensionTask.new('libsass', gem_spec) do |ext|
   ext.name = 'libsass'
   ext.ext_dir = 'ext'
   ext.lib_dir = 'lib/sassc'
+  ext.cross_compile = true
+  ext.cross_platform = %w[x86-mingw32 x64-mingw32 x86-linux x86_64-linux]
+end
+
+desc 'Compile all native gems via rake-compiler-dock (Docker)'
+task 'gem:native' do
+  require 'rake_compiler_dock'
+  RakeCompilerDock.sh "bundle && gem i rake --no-document && "\
+                      "rake cross native gem MAKE='nice make -j`nproc`'"
 end
 
 desc "Run all tests"

lib/sassc/native.rb

@@ -8,7 +8,13 @@ module Native
 
     spec = Gem.loaded_specs["sassc"]
     gem_root = spec.gem_dir
-    ffi_lib "#{gem_root}/lib/sassc/libsass.so"
+
+    ruby_version_so_path = "#{gem_root}/lib/sassc/#{RUBY_VERSION[/\d+.\d+/]}/libsass.so"
+    if File.exist?(ruby_version_so_path)
+      ffi_lib ruby_version_so_path
+    else
+      ffi_lib "#{gem_root}/lib/sassc/libsass.so"
+    end
 
     require_relative "native/sass_value"
 

sassc.gemspec

@@ -31,9 +31,10 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "test_construct"
   spec.add_development_dependency "pry"
   spec.add_development_dependency "bundler"
+  spec.add_development_dependency "rake"
   spec.add_development_dependency "rake-compiler"
+  spec.add_development_dependency "rake-compiler-dock"
 
-  spec.add_dependency "rake"
   spec.add_dependency "ffi", "~> 1.9"
 
   gem_dir = File.expand_path(File.dirname(__FILE__)) + "/"