* 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.