perf inject: Fix missing free in copy_kcore_dir()

Free string allocated by asprintf().

Fixes: d8fc0855 ("perf inject: Keep a copy of kcore_dir")
Signed-off-by: NAdrian Hunter <adrian.hunter@intel.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20220620103904.7960-1-adrian.hunter@intel.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-inject.c

@@ -891,7 +891,9 @@ static int copy_kcore_dir(struct perf_inject *inject)
 	if (ret < 0)
 		return ret;
 	pr_debug("%s\n", cmd);
-	return system(cmd);
+	ret = system(cmd);
+	free(cmd);
+	return ret;
 }
 
 static int output_fd(struct perf_inject *inject)