fix device specific fs_config on build server

fs_config function from libcutils, in order to properly set the xattr FS
used to define device specific uid, gid, permissions and capabilities,
now needs TARGET_OUT make variable to be passed explicitly to all tools
using it:
  fs_config
  fs_get_stats used by mktarball.sh
  make_ext4fs used by mkuserimg.sh
  mksquashfs used by mksquashfsimage.sh

Bug: 21989305
Bug: 22048934
Change-Id: I6caf9cf870882fce2ead93027767092c29b75ded
Signed-off-by: Thierry Strudel <tstrudel@google.com>