[llvm] Support decompressing the SHT_LLVM_BB_ADDR_MAP section. (PR #142825)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 commented:

The premerge failures look relevant:
```
zstd::compress is unavailable
```

Seems like this needs to be gated on having zstd support built into LLVM.

Also, what's the plan for compressing the section? Is there an `lld` flag that does that or something?

https://github.com/llvm/llvm-project/pull/142825