Resolve "SDK mode"

What does this MR do?

After many years, we propose a real build of Fw4SPL as a SDK. This allows to:

• create a binary package containing Fw4SPL binaries, libraries, includes and resources,
• include/link a Fw4SPL library in a non-Fw4SPL application/library,
• create a new Fw4SPL library, bundle or application outside Fw4SPL source and build tree

Closes #3 (closed)

How to test it?

You need GDCM compiled with this fix.

Then build fw4spl and enable the CMake option BUILD_SDK. Then run ninja install and ninja package, which will give you an artifact like packages/fw4spl-17.1-linux_x86_64.tar.gz.

A sample repository has been created to show how this SDK can be used. Build instructions are given there.

Some results

Additional tests to run

• Windows
• Linux
• MacOs (not tested yet)