[MIPS] Add remaining parts for building tests for MIPS

tests/callingconv_case_by_case/nacl.scons

Index: tests/callingconv_case_by_case/nacl.scons
diff --git a/tests/callingconv_case_by_case/nacl.scons b/tests/callingconv_case_by_case/nacl.scons
index e8b11b00bf192a97ac98fa0579badc5d3e5d76d5..64d91c03c5d99efa178cb2e69a93ab2bbbce53e7 100644
--- a/tests/callingconv_case_by_case/nacl.scons
+++ b/tests/callingconv_case_by_case/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()
+
 # Case-by-case calling Convention Test for PNaCl and nacl-gcc compatibility.
 
 # We make 4 modules.