[mlir][cf] Implement missing SwitchOp::build function

[alexbatashev]

This patch probably requires a proper test case, but I'm not sure where to put it. Some guidance from reviewers would be really helpful.

mlir/lib/Dialect/ControlFlow/IR/ControlFlowOps.cpp

if (!caseValues.empty()) {
     ShapedType caseValueType = VectorType::get(
         static_cast<int64_t>(caseValues.size()), value.getType());
     caseValuesAttr = DenseIntElementsAttr::get(caseValueType, caseValues);
   }
   build(builder, result, value, defaultDestination, defaultOperands,
         caseValuesAttr, caseDestinations, caseOperands);
 }
 
+void SwitchOp::build(OpBuilder &builder, OperationState &result, Value value,
+                     Block *defaultDestination, ValueRange defaultOperands,
+                     ArrayRef<int32_t> caseValues, BlockRange caseDestinations,
+                     ArrayRef<ValueRange> caseOperands) {
+  DenseIntElementsAttr caseValuesAttr;
+  if (!caseValues.empty()) {
+    ShapedType caseValueType = VectorType::get(
+        static_cast<int64_t>(caseValues.size()), value.getType());
+    caseValuesAttr = DenseIntElementsAttr::get(caseValueType, caseValues);
+  }
+  build(builder, result, value, defaultDestination, defaultOperands,
+        caseValuesAttr, caseDestinations, caseOperands);
+}
+
 /// <cases> ::= `default` `:` bb-id (`(` ssa-use-and-type-list `)`)?
 ///             ( `,` integer `:` bb-id (`(` ssa-use-and-type-list `)`)? )*
 static ParseResult parseSwitchOpCases(
     OpAsmParser &parser, Type &flagType, Block *&defaultDestination,
     SmallVectorImpl<OpAsmParser::UnresolvedOperand> &defaultOperands,
     SmallVectorImpl<Type> &defaultOperandTypes,
     DenseIntElementsAttr &caseValues,
     SmallVectorImpl<Block *> &caseDestinations,