Defer to cmake to determine the correct build command.

Instead of presuming the build system is make when generating a cmake project
instead ask cmake to invoke the build system itself.
Patch bzip2 to defer to the system cc compiler.
Merge pull request #149 from robertmaynard/bzip2_clang

Patch bzip2 to defer to the system cc compiler.
Merge pull request #148 from robertmaynard/cmake_build

Defer to cmake to determine the correct build command.
Add in support for gdal.
Add in support for kml
Make sure we build kml in release mode.
Make sure we build in release mode with shared libraries.
Merge pull request #157 from robertmaynard/gdal_pkg

Add in support for gdal.
Merge pull request #158 from robertmaynard/kml_pkg

Add in support for kml