[Android] Enable app customize/build tools works on Window Host.

Original customize/build tools are only verified on Linux Host.
They have some environment assumptions for Linux, which would
break the app build on Windows Host. What's more,
there are also some differences for default behavior of build tools,
such as: ant etc. This patch will fill the gap, make app
customize/build tools works on Window Host.

1. Fix the different path separator on different OS host.
2. Fix different default ant behavior on diefferent OS host.
3. Fix different extension for executable binary on different OS host.
4. Fix python subprocess work different on different OS host.

BUG=https://github.com/crosswalk-project/crosswalk/issues/616