Improve the build scripts

This patch made all the remaining hardcoded values into config files.

It also tested all the libraries on Android platform. Now only websockets is not working on andorid-21.
It means we can't build arm64 arch for websockets. I have already reported the issue to the official repository.

To build the webp with arm64 support on Android platform , we need also a hack method. The method was already updated in the README.md.

If you guys meet any issues, please let me know.