perf annotate: Add error log in symbol__annotate()

When users use 'perf annotate' on unsupported machines, error logs
should be printed for user feedback.

Signed-off-by: Li Huafei <lihuafei1@huawei.com>
Reviewed-by: James Clark <james.clark@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Dengcheng Zhu <dzhu@wavecomp.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Martin Liška <mliska@suse.cz>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Riccardo Mancini <rickyman7@gmail.com>
Cc: Zhang Jinhao <zhangjinhao2@huawei.com>
Link: http://lore.kernel.org/lkml/20210726123854.13463-2-lihuafei1@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/annotate.c

@@ -2192,8 +2192,10 @@ int symbol__annotate(struct map_symbol *ms, struct evsel *evsel,
 		return errno;
 
 	args.arch = arch = arch__find(arch_name);
-	if (arch == NULL)
+	if (arch == NULL) {
+		pr_err("%s: unsupported arch %s\n", __func__, arch_name);
 		return ENOTSUP;
+	}
 
 	if (parch)
 		*parch = arch;