Update build script instructions
Update build script instructions

Shorten/optimize the build script instructions and make them only copy DLLs, not including the license files unpacked from those directories.
Rust-SDL2/rust-sdl2,AngryLawyer/rust-sdl2,Rust-SDL2/rust-sdl2,Cobrand/rust-sdl2,Cobrand/rust-sdl2,Cobrand/rust-sdl2,Rust-SDL2/rust-sdl2