[lldb][ObjectFileELF] Improve error output for unsupported arch/relocations

ObjectFileELF::ApplyRelocations() considered all 32-bit input objects to be i386 and didn't provide good error messages for AArch32 objects. Please find an example in https://github.com/llvm/llvm-project/issues/61948
While we are here, let' improve the situation for unsupported architectures as well. I think we should report the error here too and not silently fail (or crash with assertions enabled).

Reviewed By: SixWeining

Differential Revision: https://reviews.llvm.org/D147627