all: add wasip1 definitions

Add wasip1 GOOS definitions to the compiler and build
definitions.

Co-authored-by: Richard Musiol <neelance@gmail.com>
Co-authored-by: Achille Roussel <achille.roussel@gmail.com>
Co-authored-by: Julien Fabre <ju.pryz@gmail.com>
Co-authored-by: Evan Phoenix <evan@phx.io>
Change-Id: I087e7ff4205a34187bbca18b1693ad911ddd1219
Reviewed-on: https://go-review.googlesource.com/c/go/+/479616


Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Auto-Submit: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
Run-TryBot: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>