LTO: Export functions referenced by non-canonical CFI jump tables

LowerTypeTests pass adds functions with a non-canonical jump table
to cfiFunctionDecls instead of cfiFunctionDefs. As the jump table
is in the regular LTO object, these functions will also need to be
exported. This change fixes the non-canonical jump table case and
adds a test similar to the existing one for canonical jump tables.

Reviewed By: pcc

Differential Revision: https://reviews.llvm.org/D103120