[lld test] Tighten ELF/pre_init_fini_array.s test

Summary:
Make use of FileCheck numeric variable to tighten symbol address checks
in ELF/pre_init_fini_array.s test.

Reviewers: khemant, compnerd, echristo, jhenderson, espindola, MaskRay

Reviewed By: MaskRay

Subscribers: emaste, MaskRay, llvm-commits, rupprecht

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D76852