The jni\native\BUILDING file in the tomcat-native-1.1.27-win32-src.zip package contains UNIX build instructions. Since this package is specific to Windows, this file should contain Windows build instructions.
In general, Windows building instructions need an update a) in native/BUILDING file b) on the site http://tomcat.apache.org/native-doc/#Building As of now, latest build instructions from Mladen are here: https://issues.apache.org/bugzilla/show_bug.cgi?id=56363#c10
Fixed for 1.2.11