[turbofan] Drop V8_TURBOFAN_BACKEND and V8_TURBOFAN_TARGET defines.

test/cctest/compiler/graph-builder-tester.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_CCTEST_COMPILER_GRAPH_BUILDER_TESTER_H_
 #define V8_CCTEST_COMPILER_GRAPH_BUILDER_TESTER_H_
 
 #include "src/v8.h"
 #include "test/cctest/cctest.h"
 
@@ skipping 250 matching lines @@
         effect_ = result;
       }
       // This graph builder does not support control flow.
       CHECK_EQ(0, op->ControlOutputCount());
     }
 
     return result;
   }
 
   virtual byte* Generate() {
-    if (!Pipeline::SupportedBackend()) return NULL;
     if (code_.is_null()) {
       Zone* zone = graph()->zone();
       CallDescriptor* desc =
           Linkage::GetSimplifiedCDescriptor(zone, this->csig_);
       code_ = Pipeline::GenerateCodeForTesting(main_isolate(), desc, graph());
 #ifdef ENABLE_DISASSEMBLER
       if (!code_.is_null() && FLAG_print_opt_code) {
         OFStream os(stdout);
         code_.ToHandleChecked()->Disassemble("test code", os);
       }
@@ skipping 16 matching lines @@
   Node* return_;
   Node** parameters_;
   MaybeHandle<Code> code_;
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CCTEST_COMPILER_GRAPH_BUILDER_TESTER_H_