libgo: Hurd portability patches

By Svante Signell.

Fixes https://gcc.gnu.org/PR93020

Change-Id: I8b52d4f7dd4cb248a2c27bdd19ee3b33666373b3
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/212409
Reviewed-by: Ian Lance Taylor <iant@golang.org>
4 files changed