Added platform check
Added platform check

The prvious version of thi code runs fin from source on Linux.
But it fails at startup when running from compiled form.

This commit fixes this.
Tests has been made for the concerned functions (splash (startup issue), resource packs and internal file chooser) using source and compiled forms.
Khroki/MCEdit-Unified,fhfuih/MCEdit-Unified,skinny121/MCEdit-TallWorlds,skinny121/MCEdit-TallWorlds,Khroki/MCEdit-Unified,Khroki/MCEdit-Unified,fhfuih/MCEdit-Unified,fhfuih/MCEdit-Unified,skinny121/MCEdit-TallWorlds