Move assert.h/assert.cc from runtime/vm to runtime/platform

runtime/bin/file_macos.cc

Index: runtime/bin/file_macos.cc
diff --git a/runtime/bin/file_macos.cc b/runtime/bin/file_macos.cc
index 3187f9040fbe1aae028490499b12ed4f90a26074..2224f0fc11b6513bed073033ad4976c6058474a9 100644
--- a/runtime/bin/file_macos.cc
+++ b/runtime/bin/file_macos.cc
@@ -2,6 +2,8 @@
 // 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>
@@ -10,7 +12,6 @@
 #include <limits.h>
 
 #include "bin/builtin.h"
-#include "bin/file.h"
 
 class FileHandle {
  public:
@@ -165,7 +166,7 @@ char* File::GetCanonicalPath(const char* pathname) {
     do {
       abs_path = realpath(pathname, NULL);
     } while (abs_path == NULL && errno == EINTR);
-    assert(abs_path == NULL || IsAbsolutePath(abs_path));
+    ASSERT(abs_path == NULL || IsAbsolutePath(abs_path));
   }
   return abs_path;
 }