Cross-compilation fix for TileraMDE-3.0.1.125620

-OPT:Olimit=0 -WOPT:lpre=off:spre=off:epre=off
tile-gcc 4.4.3 does not accept these options:

cc1: error: unrecognized command line option
"-WOPT:lpre=off:spre=off:epre=off"
Undefined MALLOC_USE_HASH macro on TileMDE3

MALLOC_USE_HASH is not defined in TileraMDE-3, but exists in
TileraMDE-2. So use macro conditionally.