and fix crash when vd_aux is invalid (#86611).
vd_version, vd_flags, vd_ndx, and vd_cnt in Elf{32,64}_Verdef are
16-bit. Change VerDef to use uint16_t instead.
vda_name specifies a NUL-terminated string. Update getVersionDefinitions
to remove some `.c_str()`.
Pull Request: https://github.com/llvm/llvm-project/pull/128434