Revert "Add BacktraceOffline for offline backtracing."

Using llvm makes libbacktrace stops building for 32 bit on linux host x86_64.

This reverts commit c9c6b6ee7735f014771d81615c0278b53d14f61c.

Change-Id: Ieb807db881d7bb3132cd09e25fd08c28766ca0a8
9 files changed