syscall: use wasi-libc tables for wasm/js target

Instead of using fake tables for errno and others, use the ones that
correspond to wasi-libc.

src/syscall/syscall_nonhosted.go

@@ -1,4 +1,4 @@
-//go:build baremetal || js || wasm_unknown
+//go:build baremetal || wasm_unknown
 
 package syscall