Allow low memory machine to build with a smaller java emulator.

This allows the default for 64 bit machines and adjusts the size
on lower memory machines. If you are on 32 bit you can't build
without this change, even using pae kernel with high mem.

Patch 5: found a better way to do this. Removed import string.
Change-Id: Iac1ef3b5db96029ca62897f6b64646bf6224e752