[llvm] [DWARF5][COFF] Fix wrong relocation in .debug_line (PR #83773)

[Fangrui Song via llvm-commits]

MaskRay wrote:

This needs a test. https://maskray.me/blog/2021-08-08-toolchain-testing#i-dont-know-where-to-add-a-test

> You can comment out code that your patch has modified, or make an intentional mistake, then run the whole testsuite to locate relevant tests. You can use git log -- file to learn the history of these tests.

If you are still unsure, edit the description to include some C example so that folks can suggest how to craft a test. I believe the issue (object file format related) is better demonstrated as code.

https://github.com/llvm/llvm-project/pull/83773