[regexp] do not include irregexp interpreter by default.

src/regexp/interpreter-irregexp.cc

 // Copyright 2011 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.
 
 // A simple interpreter for the Irregexp byte code.
 
+#ifdef V8_INTERPRETED_REGEXP
+
 #include "src/regexp/interpreter-irregexp.h"
 
 #include "src/ast/ast.h"
 #include "src/regexp/bytecodes-irregexp.h"
 #include "src/regexp/jsregexp.h"
 #include "src/regexp/regexp-macro-assembler.h"
 #include "src/unicode.h"
 #include "src/utils.h"
 
 namespace v8 {
 namespace internal {
 
-
 typedef unibrow::Mapping<unibrow::Ecma262Canonicalize> Canonicalize;
 
 static bool BackRefMatchesNoCase(Canonicalize* interp_canonicalize,
                                  int from,
                                  int current,
                                  int len,
                                  Vector<const uc16> subject) {
   for (int i = 0; i < len; i++) {
     unibrow::uchar old_char = subject[from++];
     unibrow::uchar new_char = subject[current++];
@@ skipping 582 matching lines @@
                     code_base,
                     subject_vector,
                     registers,
                     start_position,
                     previous_char);
   }
 }
 
 }  // namespace internal
 }  // namespace v8
+
+#endif  // V8_INTERPRETED_REGEXP