cudatoolkit: Multiple output improvements

* Add a "lib" output containing (for the moment) only libOpenCL. This
  reduces the closure size of opensubdiv and blender by about 2 GiB.

* Add a "doc" output (about ~200 MiB).

* Remove the "sdk" output since it was worse than useless: all of the
  "sdk" output was also included in "out", so it actually increased
  disk space usage.

* Run patchelf on ELF binaries only.