plugin can't load with -trimpath TiDB-server in go1.13

[lysu]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?
   If possible, provide a recipe for reproducing the error.

Thx wph95's report

build load conn_example plugin in TiDB repo using go1.13, will meet

'2019/10/24 21:33:56.735 terror.go:342: [fatal] plugin.Open(~/Work/lab/tidb/plugin/out/conn_ip_example-1"): plugin was built with a different version of package internal/cpu'

this is introduced by #12639 that add -trimpath in make file.

2. What did you expect to see?

load success

3. What did you see instead?

load failure

4. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?

4.0 alpha, master

[lysu]

there are a go issue golang/go#31278 (comment) related to this and didn't fix.

so It's better keep 1.12 or remove -trimpath to build TiDB-server that need load plugin