Recently, I was playing for a while with Brian’s new OGR LIBKML driver and I integrated it with GDAL/OGR build system, so it’s more convenient to build, test and use it. The complete tree is available in GDAL sandbox in mloskot/winkey-libkml. (It is just a give it a try-like prototype and I don’t actively maintain this branch myself. Hopefully, Brian will take it over.)
By the way, I crafted AX_LIB_LIBKML macro for Autoconf. This macros checks for headers and libraries of specified version (or newer) of Google libkml library and defines compilation and linking flags.
I submitted the macro to GNU Autoconf Archive. It is the new incarnation of well-known autoconf-archive.cryp.to. Peter Simons announced not long time ago that
The archive has moved to Savannah: http://www.nongnu.org/autoconf-archive/. Version 2009-04-26 was the last to be released at autoconf-archive.cryp.to.
Happy detecting libkml!