[lld] [LLD][COFF] Detect weak reference cycles. (PR #104463)

[Fangrui Song via llvm-commits]

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+REQUIRES: x86
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MaskRay wrote:

I think COFF doesn't have ELF's weak references. COFF only has weak externals, similar to ELF's weak definitions.

I'd use `weak-external-cycle.test` to be beside `weak-external{,2,3}.test`

https://github.com/llvm/llvm-project/pull/104463