[clang] [OpenACC] Implement 'if' clause for Compute Constructs (PR #88411)

[Alexey Bataev via cfe-commits]

================
@@ -7425,6 +7425,12 @@ void ASTRecordWriter::writeOpenACCClause(const OpenACCClause *C) {
     writeEnum(DC->getDefaultClauseKind());
     return;
   }
+  case OpenACCClauseKind::If: {
+    const auto *IC = cast<OpenACCIfClause>(C);
+    writeSourceLocation(IC->getLParenLoc());
+    AddStmt(const_cast<Expr *>(IC->getConditionExpr()));
----------------
alexey-bataev wrote:

```suggestion
    auto *IC = cast<OpenACCIfClause>(C);
    writeSourceLocation(IC->getLParenLoc());
    AddStmt(IC->getConditionExpr());
```


https://github.com/llvm/llvm-project/pull/88411