wasi preview 2 support (#4027)

* all: wasip2 support

Co-authored-by: Randy Reddig <randy.reddig@fastly.com>

src/syscall/env_wasip2.go

@@ -0,0 +1,11 @@
+//go:build wasip2
+
+package syscall
+
+func Environ() []string {
+	var env []string
+	for k, v := range libc_envs {
+		env = append(env, k+"="+v)
+	}
+	return env
+}