games/tome4: fix build on powerpc

Force GCC:
In file included from ../src/luajit2/src/host/buildvm_lib.c:6:
In file included from ../src/luajit2/src/host/buildvm.h:16:
../src/luajit2/src/lj_arch.h:295:2: error: "Need at least GCC 4.3 or newer"