ld64.lld: eh frame crash for watchOS arm64_32

[keith]

This might just be a tracking issue for this FIXME:

llvm-project/lld/MachO/Arch/ARM64_32.cpp

Line 102 in 11e5275

subtractorRelocType = GENERIC_RELOC_INVALID; // FIXME

But I found that this line crashed:

llvm-project/lld/MachO/EhFrame.cpp

Lines 118 to 119 in 11e5275

	Reloc subtrahendReloc(target->subtractorRelocType, /*pcrel=*/false, length,
	off, /*addend=*/0, subtrahend);

When linking realm-swift for watchOS arm64_32. Here's a reproducer: https://drive.google.com/file/d/1xzGsPZHKCs7s_Vj_7thccboMG-7vVrGb/view?usp=sharing (I didn't try to reduce)

If this is expected for now maybe we should just ignore eh frames for this arch for now? To unblock locally I just deleted

llvm-project/lld/MachO/InputFiles.cpp

Lines 1136 to 1137 in 11e5275

	if (ehFrameSection)
	registerEhFrames(*ehFrameSection);

[llvmbot]

@llvm/issue-subscribers-lld-macho

[int3]

Hmm we should probably just fix the subtractorRelocType = GENERIC_RELOC_INVALID; thing. I can take a look at it when I get back in September