[mlir] Forward listeners when utilizing scf::IfOp::get*BodyBuilder.

[tpopp]

Summary

Without this PatternRewriting infrastructure does not know of modifications and
cannot properly legalize nor rollback changes.

[ftynse]

Thanks!

mlir/include/mlir/Dialect/SCF/SCFOps.td

let builders = [
     OpBuilder<
         "OpBuilder &builder, OperationState &result, Value cond, "
         "function_ref<void(OpBuilder &, Location)> thenBuilder "
         "    = buildTerminatedBody, "
         "function_ref<void(OpBuilder &, Location)> elseBuilder = nullptr">
   ];
 
   let extraClassDeclaration = [{
-    OpBuilder getThenBodyBuilder() {
+    OpBuilder getThenBodyBuilder(OpBuilder::Listener *listener = nullptr) {
       Block* body = getBody(0);
-      return results().empty() ? OpBuilder::atBlockTerminator(body)
-                               : OpBuilder::atBlockEnd(body);
+      return results().empty() ? OpBuilder::atBlockTerminator(body, listener)
+                               : OpBuilder::atBlockEnd(body, listener);
     }
-    OpBuilder getElseBodyBuilder() {
+    OpBuilder getElseBodyBuilder(OpBuilder::Listener *listener = nullptr) {
       Block* body = getBody(1);
-      return results().empty() ? OpBuilder::atBlockTerminator(body)
-                               : OpBuilder::atBlockEnd(body);
+      return results().empty() ? OpBuilder::atBlockTerminator(body, listener)
+                               : OpBuilder::atBlockEnd(body, listener);
     }
   }];
 }
 
 def ParallelOp : SCF_Op<"parallel",
     [AttrSizedOperandSegments,
      DeclareOpInterfaceMethods<LoopLikeOpInterface>,
      RecursiveSideEffects,