llvm3.3: Disable auto -dbg packages

* set NOAUTOPACKAGEDEBUG to disable automatic creation of -dbg FILES split
* it doesn't work well with our do_split_packages calls and in the end breaks
  installing llvm3.3-dbg (e.g. when you enable IMAGE_GEN_DEBUGFS)
* it shows a bit ugly error where multiple messages are written over
  each other:
WARNING: [log_check] In line: [ConfiCollected errors:
]
WARNING: [log_check] luneos-dev-image: found an error message in the logfile (keyword 'Collected errors'):
[log_check] ConfiCollected errors:

ERROR:
ConfiCollected errors:

 * satisfy_dependencies_for: Cannot satisfy the following dependencies for llvm3.3-dbg:

 *      libllvm3.3-lto-dbg *    libllvm3.3-llvm-3.3-dbg *

 * opkg_install: Cannot install package llvm3.3-dbg.

guring gstreamer1.0-libav-dbg.

  but the main point is that do_split_packages returns some package
  names of packages which in the end aren't created, because there
  are no files in them after other -dbg packages eat them all due
  to automatic -dbg creation

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>