perf symbols: Don't try to read the build-id twice

In __dsos__read_build_ids if the dso already had its build-id read,
don't try again.

Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/symbol.c

@@ -1131,6 +1131,10 @@ bool __dsos__read_build_ids(struct list_head *head, bool with_hits)
 	list_for_each_entry(pos, head, node) {
 		if (with_hits && !pos->hit)
 			continue;
+		if (pos->has_build_id) {
+			have_build_id = true;
+			continue;
+		}
 		if (filename__read_build_id(pos->long_name, pos->build_id,
 					    sizeof(pos->build_id)) > 0) {
 			have_build_id	  = true;