Unbreak Mac build.

src/d8-posix.cc

 // Copyright 2009 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.
 
 #include <errno.h>
 #include <fcntl.h>
+#include <signal.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/select.h>
 #include <sys/stat.h>
 #include <sys/time.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <unistd.h>
 
 #include "src/d8.h"
@@ skipping 688 matching lines @@
                 FunctionTemplate::New(isolate, UnsetEnvironment));
   os_templ->Set(String::NewFromUtf8(isolate, "umask"),
                 FunctionTemplate::New(isolate, SetUMask));
   os_templ->Set(String::NewFromUtf8(isolate, "mkdirp"),
                 FunctionTemplate::New(isolate, MakeDirectory));
   os_templ->Set(String::NewFromUtf8(isolate, "rmdir"),
                 FunctionTemplate::New(isolate, RemoveDirectory));
 }
 
 }  // namespace v8