This stubs all remaining syscalls for `GOARCH=wasm GOOS=js` to return
ENOSYS, instead of panic'ing. This allows us to see the parameters it
receives.
For example:
```
==> go.syscall/js.valueCall(fs.truncate(path=/tmp/_Go_TestTruncate135754730,length=0))
<== (err=function not implemented,ok=false)
```
Signed-off-by: Adrian Cole <adrian@tetrate.io>