Fix a naming typo for source_build
Fix a naming typo for source_build

When parsing the last_install, the variable name is supposed to be
*source_build* instead of *source_version*.

Bug: 28658632
Change-Id: I1e0ed7150e04885f904b6a3efa18bd5cfe17cc96

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base