IIS serve pre-compressed static gzip files

Web.config

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <system.webServer>
    <staticContent>
      <clientCache cacheControlMode="UseExpires" httpExpires="Tue, 19 Jan 2038 03:14:07 GMT" />
      <mimeMap fileExtension=".js.gz" mimeType="application/javascript" />
    </staticContent>
  </system.webServer>
  <location path="gz">
    <system.webServer>
      <urlCompression doStaticCompression="false" doDynamicCompression="false" dynamicCompressionBeforeCache="false" />
      <httpProtocol>
         <customHeaders>
            <add name="content-encoding" value="gzip" />
         </customHeaders>
      </httpProtocol>
    </system.webServer>
  </location>
</configuration>