cmd/link: add support for trampoline insertation on loong64

cmd/link: add support for trampoline insertation on loong64

Change-Id: I58c861d8403a77c1f3b55207d46076ba76eb1d45
Reviewed-on: https://go-review.googlesource.com/c/go/+/540755
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: sophie zhao <zhaoxiaolin@loongson.cn>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Qiqi Huang <huangqiqi@loongson.cn>