Fix overflow testing in sbrk. am: 1944780b62 am: 3a5ebf3154  -s ours am: d95336ac42 am: 0993319651 am: 0ae30d9af8 am: 83b0671a33
am: 10a48fb557

* commit '10a48fb5576d44326e35ee01d6163ba78faab9e4':
  Fix overflow testing in sbrk.

Change-Id: Ie5de1ba25e3a769ff57bd9280ae4d4d9625fe4ee