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_libc_wasi.go

@@ -1,4 +1,6 @@
-//go:build wasip1 || wasip2
+//go:build js || wasip1 || wasip2
+
+// Note: also including js in here because it also uses wasi-libc.
 
 package syscall