using a native extension to get win-file gem installed on windows. its another hook for people to jump through to install the devtools, but...

Author: adamgoucher

chemistrykit.gemspec

@@ -17,8 +17,5 @@ Gem::Specification.new do |s|
   s.add_dependency "selenium-webdriver", "~> 2.27.2"
   s.add_dependency "ci_reporter", "~> 1.8.3"
 
-  # # A user on a Windows platform is notified that they need to install the following gems manually.
-  # platforms :mswin do
-  #   s.add_dependency "win32-file", "~> 0.6.8"
-  # end
+  s.extensions = 'ext/mkrf_conf.rb'
 end

ext/mkrf_conf.rb

@@ -0,0 +1,22 @@
+require 'rubygems'
+require 'rubygems/command.rb'
+require 'rubygems/dependency_installer.rb'
+require 'rbconfig'
+
+begin
+  Gem::Command.build_args = ARGV
+rescue NoMethodError
+end 
+
+inst = Gem::DependencyInstaller.new
+begin
+  if RbConfig::CONFIG['host_os'] =~ /mswin|win|mingw/
+    inst.install  "win32-dir", "~> 0.4.1"
+  end
+rescue
+  exit(1)
+end 
+
+f = File.open(File.join(File.dirname(__FILE__), "Rakefile"), "w")   # create dummy rakefile to indicate success
+f.write("task :default\n")
+f.close