[llvm] [DWARFLinker] Handle empty sequences when processing `DW_AT_LLVM_stmt_sequence` attributes (PR #132875)

[via llvm-commits]

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alx32 wrote:

I think there are 3 main approaches here:
1. Follow existing pattern (check in binaries + script) - i.e. the current version of the PR
2. Switch the test to fully use the `update_test_body.py` approach and instead of checking in binaries, check in the `.yaml` of the binary. ([Example](https://github.com/alx32/llvm-project/blob/main/llvm/test/tools/llvm-gsymutil/ARM_AArch64/macho-gsym-merged-callsites-dsym.yaml)).
3. Use a hybrid approach where we use `update_test_body.py` to generate the binaries to check in (I don't think there is currently any test using this method).

For this small fix I went with #1 but I am OK to change it to be either way. I'll let @JDevlieghere as the code owner to decide which approach is preferable. 

https://github.com/llvm/llvm-project/pull/132875