[lld] [lld-macho] Include branch extension thunks in linker map (PR #120496)

[Tom Stellard via llvm-commits]

tstellar wrote:

I gathered some stats on my x86_64 machine with `/usr/bin/time -v  ./lld-build/bin/llvm-lit -v lld/test/MachO/arm64-thunks.s 2>&1| grep -e "Testing Time" -e "Maximum resident set size"`

Before https://github.com/llvm/llvm-project/commit/162814a7ec00e2c89693f96568b72956d1bf2f0f:
```
Testing Time: 4.56s
        Maximum resident set size (kbytes): 1666472
```
After https://github.com/llvm/llvm-project/commit/162814a7ec00e2c89693f96568b72956d1bf2f0f:
```
Testing Time: 17.61s
        Maximum resident set size (kbytes): 2984488
```

So a pretty significant increase in memory usage and run time as well.  I would consider this kind of run time increase a regression on all targets.  Is there anything that can be done to speed up the tests/reduce the memory usage?

https://github.com/llvm/llvm-project/pull/120496