[MIPS] Add remaining parts for building tests for MIPS

tests/thread_capture/nacl.scons

Index: tests/thread_capture/nacl.scons
diff --git a/tests/thread_capture/nacl.scons b/tests/thread_capture/nacl.scons
index 21aeb7a3a42a134902605f1d123a3fe7ca28137b..1b20d02584e4a75f805196c642509f31315f9534 100644
--- a/tests/thread_capture/nacl.scons
+++ b/tests/thread_capture/nacl.scons
@@ -31,6 +31,9 @@ if trusted_env.Bit('linux') or trusted_env.Bit('mac'):
   elif env.Bit('target_arm'):
     test_injection_files += [
       'arch/arm/thread_capture_test_injection.c']
+  elif env.Bit('target_mips32'):
+     test_injection_files += [
+      'arch/mips/thread_capture_test_injection.c']
   else:
     raise Exception('Unsupported target')