Add missing file required by Expat 2.2.2

Expat configure fails without this file.

See https://github.com/wxWidgets/wxWidgets/pull/524

src/expat/run.sh.in

@@ -0,0 +1,12 @@
+#! /usr/bin/env bash
+# Copyright (C) 2017 Expat development team
+# Licensed under the MIT license
+
+case "@host@" in
+*-mingw*)
+    exec wine "$@"
+    ;;
+*)
+    exec "$@"
+    ;;
+esac