Emit unwind information in .debug_frame section when .cfi_sections .debug_frame intri...

Emit unwind information in .debug_frame section when .cfi_sections .debug_frame intrinsic is used

The .cfi_sections .debug_frame intrinsic is used to emit .debug_frame
section. This directive tells the assembler to write out a section of
debug frame data. AArch64 is a platform where eh_frame is not needed for
unwind information. Unfortunately, that means that even when the
.cfi_sections .debug_frame intrinsic is used, the compiler skips
emitting the CIE's and FDE's in the debug_frame section. This patch
address that issue by making sure that the emission of CIE's and FDE's
are only skipped if the unwind information does not require a
debug_frame section and is a platform where the eh_frame can be skipped.

Differential Revision: https://reviews.llvm.org/D147980