[lld] [lld] Add support for EC code map. (PR #69101)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

FWIW, I think this commit caused the following warnings with GCC:
```
../../lld/COFF/Writer.cpp: In member function ‘void {anonymous}::Writer::assignAddresses()’:
../../lld/COFF/Writer.cpp:563:18: warning: ‘last’ is used uninitialized [-Wuninitialized]
  563 |   Chunk *first, *last;
      |                  ^~~~
../../lld/COFF/Writer.cpp:563:10: warning: ‘first’ is used uninitialized [-Wuninitialized]
  563 |   Chunk *first, *last;
      |          ^~~~~
```

https://github.com/llvm/llvm-project/pull/69101