Few tweaks to the rakefile to permit native gems compilation with the proto files generation.

ruby/Gemfile.lock

 PATH
   remote: .
   specs:
-    google-protobuf (3.0.0.alpha.5.0)
+    google-protobuf (3.0.0.alpha.5.0.5)
 
 GEM
   remote: https://rubygems.org/

ruby/Rakefile

@@ -5,35 +5,6 @@ require "rake/testtask"
 
 spec = Gem::Specification.load("google-protobuf.gemspec")
 
-if RUBY_PLATFORM == "java"
-  if `which mvn` == ''
-    raise ArgumentError, "maven needs to be installed"
-  end
-  task :clean do
-    system("mvn clean")
-  end
-
-  task :compile do
-    system("mvn package")
-  end
-else
-  Rake::ExtensionTask.new("protobuf_c", spec) do |ext|
-    ext.ext_dir = "ext/google/protobuf_c"
-    ext.lib_dir = "lib/google"
-    ext.cross_compile = true
-    ext.cross_platform = [
-      'x86-mingw32', 'x64-mingw32',
-      'x86_64-linux', 'x86-linux',
-      'universal-darwin'
-    ]
-  end
-
-  task 'gem:windows' do
-    require 'rake_compiler_dock'
-    RakeCompilerDock.sh "bundle && rake cross native gem RUBY_CC_VERSION=2.3.0:2.2.2:2.1.6"
-  end
-end
-
 well_known_protos = %w[
   google/protobuf/any.proto
   google/protobuf/api.proto
@@ -55,13 +26,46 @@ proto2_protos = %w[
 
 genproto_output = []
 
-well_known_protos.each do |proto_file|
+unless ENV['IN_DOCKER'] == 'true'
+  well_known_protos.each do |proto_file|
     input_file = "../src/" + proto_file
     output_file = "lib/" + proto_file.sub(/\.proto$/, ".rb")
     genproto_output << output_file
     file output_file => input_file do |file_task|
       sh "../src/protoc -I../src --ruby_out=lib #{input_file}"
     end
+  end
+end
+
+if RUBY_PLATFORM == "java"
+  if `which mvn` == ''
+    raise ArgumentError, "maven needs to be installed"
+  end
+  task :clean do
+    system("mvn clean")
+  end
+
+  task :compile do
+    system("mvn package")
+  end
+else
+  Rake::ExtensionTask.new("protobuf_c", spec) do |ext|
+    ext.ext_dir = "ext/google/protobuf_c"
+    ext.lib_dir = "lib/google"
+    ext.cross_compile = true
+    ext.cross_platform = [
+      'x86-mingw32', 'x64-mingw32',
+      'x86_64-linux', 'x86-linux',
+      'universal-darwin'
+    ]
+  end
+
+  task 'gem:windows' do
+    require 'rake_compiler_dock'
+    RakeCompilerDock.sh "bundle && IN_DOCKER=true rake cross native gem RUBY_CC_VERSION=2.3.0:2.2.2:2.1.5:2.0.0"
+  end
+
+  task 'gem:native' => [:genproto, 'gem:windows']
 end
 
 

ruby/google-protobuf.gemspec

 Gem::Specification.new do |s|
   s.name        = "google-protobuf"
-  s.version     = "3.0.0.alpha.5.0"
+  s.version     = "3.0.0.alpha.5.0.5"
   s.licenses    = ["BSD"]
   s.summary     = "Protocol Buffers"
   s.description = "Protocol Buffers are Google's data interchange format."