Minimal compilation fix for Windows.

lib/capybara_webkit_builder.rb

@@ -30,11 +30,20 @@ module CapybaraWebkitBuilder
   end
 
   def makefile
-    system("LANG='en_US.UTF-8' #{qmake_bin} -spec #{spec}")
+    system("#{make_env_variables} #{qmake_bin} -spec #{spec}")
   end
 
   def qmake
-    system("LANG='en_US.UTF-8' #{make_bin} qmake")
+    system("#{make_env_variables} #{make_bin} qmake")
+  end
+
+  def make_env_variables
+    case RbConfig::CONFIG['host_os']
+    when /mingw32/
+      ''
+    else
+      "LANG='en_US.UTF-8'"
+    end
   end
 
   def path_to_binary