[Sema] Produce diagnostics for attribute 'trivial_abi' that appears
after the closing brace of a class declaration.

Merge the two call sites of checkIllFormedTrivialABIStruct and sink it
into CheckCompletedCXXClass so that it is called after the attribute has
been attached to the CXXRecordDecl.

rdar://problem/40873297

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@335021 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed