Added premake run scripts for linux and osx

premake/gmake_linux.sh

@@ -0,0 +1,3 @@
+#!/bin/bash
+
+./premake5_linux gmake --file=demboyz.lua

premake/gmake_osx.sh

@@ -0,0 +1,3 @@
+#!/bin/bash
+
+./premake5_osx gmake --file=PGTA.lua