[MIPS] Add remaining parts for building tests for MIPS

tests/gdb/nacl.scons

Index: tests/gdb/nacl.scons
diff --git a/tests/gdb/nacl.scons b/tests/gdb/nacl.scons
index cc7ab4e8ee2ff2cdc0b608d1ec5f749ca3b47b40..b037e916e6836c814aff24febcfb79e4d3e0bd71 100644
--- a/tests/gdb/nacl.scons
+++ b/tests/gdb/nacl.scons
@@ -8,12 +8,12 @@ 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.