[llvm-objdump] Replace array_pod_sort with llvm::stable_sort

llvm-objdump.cpp has 3 array_pod_sort() calls used for symbolization.
array_pod_start() calls qsort() internally and can have different
behaviors across different libcs. Use llvm::stable_sort instead.

Reviewed By: davidb, thopre

Differential Revision: https://reviews.llvm.org/D76739