perf record: Improve error message of -p not_existing_pid

When one uses -p $not_existing_pid, the output of --help is printed:

  $ perf record -p 123456789 2>&1 | head -n3

   Usage: perf record [<options>] [<command>]
      or: perf record [<options>] -- <command> [<options>]

Let's change it something similar what perf top -p $not_existing_pid
prints:

  $ ./perf top -p 123456789 --stdio
  Error:
  Couldn't create thread/CPU maps: No such process

Newly suggested error message:

  $ ./perf record -p 123456789
  Couldn't create thread/CPU maps: No such process
Signed-off-by: Martin Liška <mliska@suse.cz>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: http://lore.kernel.org/lkml/8e00eda1-4de0-2c44-ce67-d4df48ac1f7c@suse.czSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-record.c

@@ -3996,8 +3996,15 @@ int cmd_record(int argc, const char **argv)
 		arch__add_leaf_frame_record_opts(&rec->opts);
 
 	err = -ENOMEM;
-	if (evlist__create_maps(rec->evlist, &rec->opts.target) < 0)
-		usage_with_options(record_usage, record_options);
+	if (evlist__create_maps(rec->evlist, &rec->opts.target) < 0) {
+		if (rec->opts.target.pid != NULL) {
+			pr_err("Couldn't create thread/CPU maps: %s\n",
+				errno == ENOENT ? "No such process" : str_error_r(errno, errbuf, sizeof(errbuf)));
+			goto out;
+		}
+		else
+			usage_with_options(record_usage, record_options);
+	}
 
 	err = auxtrace_record__options(rec->itr, rec->evlist, &rec->opts);
 	if (err)