[llvm] [DebugInfo][DWARF] Set is_stmt on first non-line-0 instruction in BB (PR #105524)

[J. Ryan Stinnett via llvm-commits]

https://github.com/jryans approved this pull request.

Seems like a good tweak, looks good overall to me.

https://github.com/llvm/llvm-project/pull/105524