Fixed broken build under GCC 5.4.

[sfuniak]

Summary

This diff fixes broken build caused by D108550. Under GCC 5, auto lambdas that capture this require this-> for member calls.

[bondhugula]

Is there a bot to check to verify this fixes the gcc5 build?

[sfuniak]

@bondhugula I am not sure, but I built this with GCC 5.4 myself. The code compiled, and all the tests passed.

[mehdi_amini]

Is there a bot to check to verify this fixes the gcc5 build?

Yes, but on staging: https://lab.llvm.org/staging/#/builders/190

mlir/lib/Conversion/PDLToPDLInterp/PDLToPDLInterp.cpp

Block *PatternLowering::generateMatcher(MatcherNode &node, Region &region) {
   // If this value corresponds to an operation, record that we are going to use
   // its location as part of a fused location.
   bool isOperationValue = val && val.getType().isa<pdl::OperationType>();
   if (isOperationValue)
     locOps.insert(val);
 
   // Dispatch to the correct method based on derived node type.
   TypeSwitch<MatcherNode *>(&node)
-      .Case<BoolNode, SwitchNode>(
-          [&](auto *derivedNode) { generate(derivedNode, currentBlock, val); })
+      .Case<BoolNode, SwitchNode>([&](auto *derivedNode) {
+        this->generate(derivedNode, currentBlock, val);
+      })
       .Case([&](SuccessNode *successNode) {
         generate(successNode, currentBlock);
       });
 
   // Pop all the failure blocks that were inserted due to nesting of
   // pdl_interp.iterate.
   while (failureBlockStack.back() != failureBlock) {
     failureBlockStack.pop_back();