[WinEH] Emit the LSDA even if no lpads remain but outlining occurred

The outlined funclets call intrinsics which reference labels from the
LSDA. This situation can easily arise in small functions with a single
cleanup at -O0, where Clang marks a definition as nounwind, and then
WinEHPrepare "discovers" that the landingpad is dead by accident and
deletes it.

We now need to ask the LLVM IR Function for it's personality directly,
rather than going through MachineModuleInfo.

Fixes PR23892.

llvm-svn: 242063