Add support for writing 64-bit symbol tables for archives when offsets become too large for 32-bit

This should fix https://bugs.llvm.org//show_bug.cgi?id=34189

This change makes it so that if writing a K_GNU style archive, you need
to output a > 32-bit offset it should output in K_GNU64 style instead.

Differential Revision: https://reviews.llvm.org/D36812

llvm-svn: 316805