Fix overflow testing in sbrk. am: 1944780b62
am: 3a5ebf3154  -s ours

* commit '3a5ebf3154f4ff22b9196f0cc43986a458b6cadc':
  Fix overflow testing in sbrk.

Change-Id: I48cdfd2a6d05fa81bcd3dc3415c078b5f79c1f0f