This assertion triggered when we have two base classes sharing the same offset
and the first base is empty and the second class is non-empty.
Remove it for correctness.
I can't add a test case for this because -foverride-record-layout doesn't read
base class info at all. I can add that support later for testing if needed.
Reviewed By: rnk
Differential Revision: https://reviews.llvm.org/D152472