Fix infinite recursion when dealing with cyclic library dependencies.

bin/file_macos.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. 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 <sys/stat.h>
 #include <unistd.h>
 #include <libgen.h>
 
@@ skipping 100 matching lines @@
     return false;
   }
 }
 
 
 bool File::IsAbsolutePath(const char* pathname) {
   return (pathname != NULL && pathname[0] == '/');
 }
 
 
+char* File::GetCanonicalPath(const char* pathname) {
+  char* abs_path = NULL;
+  if (pathname != NULL) {
+    abs_path = realpath(pathname, NULL);
+    assert(abs_path == NULL || IsAbsolutePath(abs_path));
+  }
+  return abs_path;
+}
+
+
 const char* File::PathSeparator() {
   return "/";
 }
 
 
 const char* File::StringEscapedPathSeparator() {
   return "/";
 }