Commit ad23e152 caused generate_nlmsg to be always missing:
$ make alltests
make: ./tools/generate_nlmsg: Command not found
Create testclean: to remove only results directory.
Fixes: ad23e152 testsuite: remove all temp files and implement make clean
Signed-off-by: Petr Vorel <petr.vorel@gmail.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>