Add proper Intructions on building FFmpeg Executable binary with static linking

[Shabinder]

This is somewhat a feature request.

As you have mentioned in few issues you plan to do this, I thought having this in the tracker will help.

[Shabinder]

These changes do work if someone wants to do the same until instructions are added: https://github.com/Javernaut/ffmpeg-android-maker/issues/49#issuecomment-871316847

[bugparty]

I will add this option when I have time