This eliminates the 'wasi' build tag in favor of 'GOOS=wasip1', introduced in Go 1.21.
For backwards compatablity, -target=wasi is a synonym for -target=wasip1.
This basically reverts https://github.com/tinygo-org/tinygo/pull/3357
and replaces it with a different mechanism to get to the same goal.
I do not think filtering tags like this is a good idea: it's the wrong
part of the compiler to be concerned with such tags (that part sets
tags, but doesn't modify existing tags). Instead, I've written the
//go:build lines in such a way that it has the same effect: WASI
defaults to leveldb, everything else defaults to fnv, and it's possible
to override the default using build tags.
We have an optimization for this specific pattern, but it's really just
a hack. With the addition of unsafe.Add in Go 1.17 we can directly
specify the intent instead and eventually remove this special case.
The code is also easier to read.
Randy Reddig
Ayke van Laethem
Yurii Soldak
Damian Gryski