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

[Stephen Tozer via llvm-commits]

SLTozer wrote:

Hm, another [buildbot error](https://lab.llvm.org/buildbot/#/builders/160/builds/4142) - this time `createMCCodeEmitter failed`, which seems like it will also be a trivial fix, but I'll revert for now.

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