[llvm] [DebugInfo] Fix line 0 records incorrectly having is_stmt set (PR #166627)

[Orlando Cazalet-Hyams via llvm-commits]

================
@@ -2199,12 +2199,16 @@ void DwarfDebug::beginInstruction(const MachineInstr *MI) {
   if (DL.getLine() == 0 && LastAsmLine == 0)
     return;
   if (MI == PrologEndLoc) {
-    Flags |= DWARF2_FLAG_PROLOGUE_END | DWARF2_FLAG_IS_STMT;
+    Flags |= DWARF2_FLAG_PROLOGUE_END;
+    // Don't set is_stmt for line 0
+    if (DL.getLine() != 0)
+      Flags |= DWARF2_FLAG_IS_STMT;
     PrologEndLoc = nullptr;
   }
 
   if (ScopeUsesKeyInstructions) {
-    if (IsKey)
+    // Don't set is_stmt for line 0
----------------
OCHyams wrote:

```suggestion
    // Don't set is_stmt for line 0.
```

https://github.com/llvm/llvm-project/pull/166627