[MIPS] Add remaining parts for building tests for MIPS

tests/callingconv/nacl.scons

Index: tests/callingconv/nacl.scons
diff --git a/tests/callingconv/nacl.scons b/tests/callingconv/nacl.scons
index d59b86aa7477aadfe1fa66ddde604b83075ff8c8..f11809fc830dcc98781450b7505270253262e36e 100644
--- a/tests/callingconv/nacl.scons
+++ b/tests/callingconv/nacl.scons
@@ -9,6 +9,11 @@ Import('env')
 if env.Bit('bitcode') and env.Bit('pnacl_generate_pexe'):
   Return()
 
+# This test is disabled for MIPS because we do not have a MIPS-enabled nacl-gcc
+# to test PNaCl against.
+if env.Bit('target_mips32'):
+  Return()
+
 # If this test is failing on the bots, you can find the seed
 # from the output of the bot. Look for "--seed=".
 # To reproduce the exact problem, set settings['seed'] below