win32: fix build g_spawn_check_exit_status() with mingw

With mingw, only gspawn-win32.c is compiled, but it is missing some
new symbols.

https://bugzilla.gnome.org/show_bug.cgi?id=679691

glib/gspawn-win32.c

@@ -211,6 +211,12 @@ g_spawn_error_quark (void)
   return g_quark_from_static_string ("g-exec-error-quark");
 }
 
+GQuark
+g_spawn_exit_error_quark (void)
+{
+  return g_quark_from_static_string ("g-spawn-exit-error-quark");
+}
+
 gboolean
 g_spawn_async_utf8 (const gchar          *working_directory,
 		    gchar               **argv,
@@ -1221,6 +1227,25 @@ g_spawn_close_pid (GPid pid)
     CloseHandle (pid);
 }
 
+gboolean
+g_spawn_check_exit_status (gint      exit_status,
+			   GError  **error)
+{
+  gboolean ret = FALSE;
+
+  if (exit_status != 0)
+    {
+      g_set_error (error, G_SPAWN_EXIT_ERROR, exit_status,
+		   _("Child process exited with code %ld"),
+		   (long) exit_status);
+      goto out;
+    }
+
+  ret = TRUE;
+ out:
+  return ret;
+}
+
 #if !defined (_WIN64)
 
 /* Binary compatibility versions that take system codepage pathnames,

glib/gspawn.c

@@ -855,7 +855,6 @@ g_spawn_check_exit_status (gint      exit_status,
 {
   gboolean ret = FALSE;
 
-#ifdef G_OS_UNIX
   if (WIFEXITED (exit_status))
     {
       if (WEXITSTATUS (exit_status) != 0)
@@ -886,15 +885,6 @@ g_spawn_check_exit_status (gint      exit_status,
 		   _("Child process exited abnormally"));
       goto out;
     }
-#else
-  if (exit_status != 0)
-    {
-      g_set_error (error, G_SPAWN_EXIT_ERROR, exit_status,
-		   _("Child process exited with code %ld"),
-		   (long) exit_status);
-      goto out;
-    }
-#endif
 
   ret = TRUE;
  out: