Make resulting cmake config relocatable

[bachp]

This change avoids hardcoded install prefix in the p8-platform-config.cmake.
Especially important when doing cross compilation with Yocto for example.

[MartijnKaijser]

Maybe try here
https://github.com/xbmc/platform

[bachp]

@MartijnKaijser Is this project dead? Or why do you suggest https://github.com/xbmc/platform?

[malard]

This project isn't dead, we will review next week, thanks for the contribution!

[bachp]

The patch landed in OpenEmbedded where it was required to build without errors.

[opdenkamp]

I haven't checked cmake's commit history, but the links in the manual to get_filename_component() suggest that this has been added in cmake 3.0, so cmake_minimum_required() needs to be updated too:

platform/CMakeLists.txt

Line 3 in 2650bb3

cmake_minimum_required(VERSION 2.8.9)

It also needs a quick rebase because of b784c04

thanks

[bachp]

I need to verify, but it could be that b784c04 made this change obsolete.