Mark calls in thunk functions as tail-call optimization candidates
When a thunk is generated with a call to the original adjusted function,
the thunk appears in the debugger call stack. We want the backend to perform
tail-call optimization on the call, to make it invisible to the debugger.
This fixes PR24235
Patch by: firstname.lastname@example.org
Differential Revision: http://reviews.llvm.org/D11476