Add import (only for functions for now) and call

comp_wasm.kp

@@ -5,6 +5,7 @@
                        true                *ARGV*)
     _ (println "out" out)
     wasm_code (module
+        (import "wasi_unstable" "fd_write" (func $fd_write (param i32 i32 i32 i32) (result i32)))
         (func $add (param $num i32) (result i32)
             (local $tmp1 i32)
             (local $tmp2 i32)
@@ -19,6 +20,14 @@
                 )
                 (br $test)
                 drop
+
+                (call $fd_write
+                      (i32.const 0) ;; file descriptor
+                      (i32.const 8) ;; *iovs
+                      (i32.const 1) ;; iovs_len
+                      (i32.const 4) ;; nwritten
+                )
+                drop
             )
             (i32.const 11)
             (local.get $tmp2)