make: add flags and fix some warnings

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
src: setfsuid / setfsgid

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
trafgen: add csum calculation, fix deadlock

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>