[MIPS] Add remaining parts for building tests for MIPS

tests/gdb/nacl.scons

 # -*- python -*-
 # Copyright (c) 2012 The Native Client 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('env')
 
 if 'TRUSTED_ENV' not in env:
   Return()
 
-if env.Bit('target_arm'):
+if env.Bit('target_arm') or env.Bit('target_mips32'):
   if env.UsingEmulator():
-    # These tests do not work under qemu-arm.
+    # These tests do not work under qemu-arm and qemu-mips32.
     Return()
-  # Use the system's ARM GDB because the NaCl toolchain does not
-  # include a copy of GDB built to run on ARM.
+  # Use the system's ARM (or MIPS) GDB because the NaCl toolchain does not
+  # include a copy of GDB built to run on ARM (or MIPS).
   env.Replace(GDB='gdb')
   # Unlike nacl-gdb, the system version of GDB does not support the
   # "nacl-irt" command.
   if env.Bit('tests_use_irt'):
     Return()
 
 # We need -O0 to make stepping predictable and read local variables/function
 # arguments that may otherwise be optimized out.
 env.Append(CCFLAGS=['-O0', '-g', '-fno-omit-frame-pointer'])
 # We need to disable PNaCl's link time optimizations so that functions
@@ skipping 136 matching lines @@
 env.TestBindsFixedTcpPort(node)
 
 node = env.CommandTest(
     'gdb_syscall_thread.out',
     extra_deps=extra_deps,
     command=['${PYTHON}', env.File('syscall_thread.py'),
              '--nexe', gdb_test_guest_thread] + test_args)
 
 env.AddNodeToTestSuite(node, test_suites, 'run_gdb_syscall_thread_test')
 env.TestBindsFixedTcpPort(node)