Fix overflow testing in sbrk. am: 1944780b62 am: 3a5ebf3154  -s ours am: d95336ac42 am: 0993319651 am: 0ae30d9af8 am: 83b0671a33 am: 10a48fb557 am: fd84d78b1e am: b4d92e1362 am: ad80daaab5
am: 7189a4ccc2

* commit '7189a4ccc23598eeca0d769bc70916b6a9fe3bf6':
  Fix overflow testing in sbrk.

Change-Id: I3ede782a21037ce189b093dc4448ac5154a11f1b