Adds deprecation messages for MIPS cross-builds

tools/gn.py

 #!/usr/bin/env python
 # Copyright 2016 The Dart 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.
 
 import argparse
 import multiprocessing
 import os
 import shutil
 import subprocess
@@ skipping 126 matching lines @@
 
 def ToGnArgs(args, mode, arch, target_os):
   gn_args = {}
 
   host_os = HostOsForGn(HOST_OS)
   if target_os == 'host':
     gn_args['target_os'] = host_os
   else:
     gn_args['target_os'] = target_os
 
+  if arch.startswith('mips'):
+    bold  = '\033[1m'
+    reset = '\033[0m'
+    print(bold + "Warning: MIPS architectures are unlikely to be supported in "
+          "upcoming releases. Please consider using another architecture "
+          "and/or file an issue explaining your specific use of and need for "
+          "MIPS support." + reset)
+
   gn_args['dart_target_arch'] = arch
   gn_args['target_cpu'] = TargetCpuForArch(arch, target_os)
   gn_args['host_cpu'] = HostCpuForArch(arch)
   crossbuild = gn_args['target_cpu'] != gn_args['host_cpu']
 
   # See: runtime/observatory/BUILD.gn.
   # This allows the standalone build of the observatory to fall back on
   # dart_bootstrap if the prebuilt SDK doesn't work.
   gn_args['dart_host_pub_exe'] = ""
 
@@ skipping 80 matching lines @@
 
 
 def ProcessOsOption(os_name):
   if os_name == 'host':
     return HOST_OS
   return os_name
 
 
 def ProcessOptions(args):
   if args.arch == 'all':
-    args.arch = 'ia32,x64,simarm,simarm64,simmips,simdbc64'
+    args.arch = 'ia32,x64,simarm,simarm64,simdbc64'
   if args.mode == 'all':
     args.mode = 'debug,release,product'
   if args.os == 'all':
     args.os = 'host,android'
   args.mode = args.mode.split(',')
   args.arch = args.arch.split(',')
   args.os = args.os.split(',')
   for mode in args.mode:
     if not mode in ['debug', 'release', 'product']:
       print "Unknown mode %s" % mode
@@ skipping 195 matching lines @@
       return 1
 
   endtime = time.time()
   if args.verbose:
     print ("GN Time: %.3f seconds" % (endtime - starttime))
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main(sys.argv))