[MS] Fix C++ destructor thunk line info for a declaration

Sometimes the MS ABI needs to emit thunks for declarations that don't
have bodies. Destructor thunks make calls to inlinable functions, so
they need line info or LLVM will complain.

Fixes PR31893

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@294465 91177308-0d34-0410-b5e6-96231b3b80d8