Fix mac dartium build

runtime/bin/utils_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 "platform/globals.h"
 #if defined(TARGET_OS_MACOS)
 
 #include <errno.h>  // NOLINT
 #include <mach/clock.h>  // NOLINT
 #include <mach/mach.h>  // NOLINT
@@ skipping 60 matching lines @@
 
 
 char* StringUtils::Utf8ToConsoleString(
     char* utf8, intptr_t len, intptr_t* result_len) {
   UNIMPLEMENTED();
   return NULL;
 }
 
 
 char* StringUtils::StrNDup(const char* s, intptr_t n) {
+  // strndup has only been added to Mac OS X in 10.7. We are supplying
+  // our own copy here if needed.
+#if !defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) || \
+    __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ <= 1060
+  intptr_t len = strlen(s);
+  if ((n < 0) || (len < 0)) {
+    return NULL;
+  }
+  if (n < len) {
+    len = n;
+  }
+  char* result = reinterpret_cast<char*>(malloc(len + 1));
+  if (result == NULL) {
+    return NULL;
+  }
+  result[len] = '\0';
+  return reinterpret_cast<char*>(memmove(result, s, len));
+#else  // !defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) || ...
   return strndup(s, n);
+#endif  // !defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) || ...
 }
 
 
 bool ShellUtils::GetUtf8Argv(int argc, char** argv) {
   return false;
 }
 
 
 static mach_timebase_info_data_t timebase_info;
 
@@ skipping 67 matching lines @@
     ASSERT(errno == EINTR);
     // Copy remainder into requested and repeat.
     req = rem;
   }
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_MACOS)