runtime, syscall: add a couple of hurd build tags

Patch by Svante Signell.

Updates https://gcc.gnu.org/PR93468

Change-Id: Ibb31bee789aaed48875698fa6286d0d8c255f36f
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/216959
Reviewed-by: Ian Lance Taylor <iant@golang.org>
2 files changed