This adds true GOOS=wasip1 support in addition to our existing
-target=wasi support. The old support for WASI isn't removed, but should
be treated as deprecated and will likely be removed eventually to reduce
the test burden.
These are used in Go 1.18's `testing/internal/testdeps`. Though the
comment says they should exist _everywhere_, there is still a build
constraint, but that seems to be fine.
Damian Gryski
leongross
Ayke van Laethem
Yurii Soldak
Dan Kegel
Elliott Sales de Andrade