tools lib traceevent: Use LDFLAGS in the build commands

So that the user can specify outside LDFLAGS values.

Keeping the CFLAGS in there as well, so we don't break existing scripts.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Herton Krzesinski <herton@redhat.com>
Cc: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Link: http://lkml.kernel.org/r/20181212091214.GC17489@krava


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>