Error out if MALLOC_IMPL is defined.
Error out if MALLOC_IMPL is defined.

Bug: http://b/26390299
Change-Id: Icd3ce6853c8207b1a9ce1f9d546a61d5b113f15a

xorware/android_build,xorware/android_build,xorware/android_build,xorware/android_build,xorware/android_build