Autoconf build scripts need updating for building on Linux, Windows

[xcom169]

Can you please post build instructions for Ubuntu like cmake, or ./configure ?

[bentorkington]

A long time ago I set up Autoconf scripts and built this project on Linux, but these scripts are now out of date with the main Xcode project.

Can someone with enough time help out and send a PR with an updated build script & instructions?

[fabiensanglard]

@bentorkington Would you be open to a PR with a CMakelist that would improve portability?

[bentorkington]

Absolutely. I'll always use Xcode as my main way of working with the project, but I don't mind which toolchain is used for building on other platforms