Let .llvm_bb_addr_map section use the same unique id as its associated .text section.

Currently, `llvm_bb_addr_map` sections are generated per section names because we use
the `LinkedToSymbol` argument of getELFSection. This will cause the address map tables of functions
grouped into the same section when `-function-sections=true -unique-section-names=false` which is not
the intended behaviour. This patch lets the unique id of every `.text` section propagate to the associated
`.llvm_bb_addr_map` section.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D92113