runtime: add support for --buildmode=c-shared on loong64
These c-shared related CLs are follow up of CLs 455016, 455017, 455018. Here we
follow the LoongArch ELF psABI v2 standard, which requires the support of the
PCALAU12I instruction.
Updates #53301
Updates #58784
Change-Id: I7f1ddbf3b2470d610f12069d147aa9b3a6a96f32
Reviewed-on: https://go-review.googlesource.com/c/go/+/425474 Reviewed-by: abner chenc <chenguoqi@loongson.cn> Reviewed-by: WANG Xuerui <git@xen0n.name> Reviewed-by: Ian Lance Taylor <iant@google.com> Reviewed-by: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>