[lld] [LLD][COFF] Deduplicate common chunks when linking COFF files. (PR #162553)

[Joshua Cranmer via llvm-commits]

jcranmer-intel wrote:

I apologize for the lack of a test with this change--I'm not exactly sure how to go about writing an LLD test for linking together multiple objects, and would like some guidance on how to do so. (I do have some source test files from https://github.com/llvm/llvm-project/issues/162148, though).

https://github.com/llvm/llvm-project/pull/162553