This changes the structure to use paths like `build/Release/lib`
instead of `build/lib/Release`, so that the `build/Release` directory
more closely mimics the structure of `build` when in single-configuration
mode.
This allows exporting (a stub function that forwards to) a
function that returns a value - it's particularly useful in
the graphics plugins for the "get_pipe_type_foo()" functions.
This also frees up CMake from needing to use any of the source
files in the metalibs/*/ directories.
rdb
Sam Edwards