Deal with symbolic links for file and directories on Mac and Linux.

runtime/bin/file_macos.cc

 // Copyright (c) 2012, 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 "bin/file.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <unistd.h>
@@ skipping 123 matching lines @@
 
 File* File::OpenStdio(int fd) {
   if (fd < 0 || 2 < fd) return NULL;
   return new File(NULL, new FileHandle(fd));
 }
 
 
 bool File::Exists(const char* name) {
   struct stat st;
   if (TEMP_FAILURE_RETRY(stat(name, &st)) == 0) {
-    return S_ISREG(st.st_mode);  // Deal with symlinks?
+    return S_ISREG(st.st_mode);
   } else {
     return false;
   }
 }
 
 
 bool File::Create(const char* name) {
   int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CREAT, 0666));
   if (fd < 0) {
     return false;
@@ skipping 78 matching lines @@
   int result = fstat(fd, &buf);
   if (result == -1) {
     FATAL2("Failed stat on file descriptor %d: %s", fd, strerror(errno));
   }
   if (S_ISCHR(buf.st_mode)) return kTerminal;
   if (S_ISFIFO(buf.st_mode)) return kPipe;
   if (S_ISSOCK(buf.st_mode)) return kSocket;
   if (S_ISREG(buf.st_mode)) return kFile;
   return kOther;
 }