lib/oe/recipeutils: fix find_layerdir() to return absolute paths
find_layerdir() should really return absolute paths, so make it do so.
This fixes devtool finish not deleting files it should do after devtool
upgrade if the specified path is relative, since the devtool finish code
was assuming that find_layerdir() was returning an absolute path.
Fixes [YOCTO #12318].
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
