[MIPS] Fix missing definitions for MIPS arch in build and driver scripts

pnacl/build.sh

Index: pnacl/build.sh
diff --git a/pnacl/build.sh b/pnacl/build.sh
index dbd2190bfd62af3c0bc043fb641dfd5414e83dae..2f9bf45805f5b7ab1732529901273768a7b31cc4 100755
--- a/pnacl/build.sh
+++ b/pnacl/build.sh
@@ -1459,6 +1459,7 @@ libgcc_eh-newlib() {
   # This is a temporary situation. Eventually, libgcc_eh won't depend
   # on LibC, and it will be built once for each architecture in a neutral way.
   libgcc_eh arm    newlib
+  libgcc_eh mips32 newlib
   libgcc_eh x86-32 newlib
   libgcc_eh x86-64 newlib
 }
@@ -1593,6 +1594,7 @@ install-unwind-header() {
 compiler-rt-all() {
   StepBanner "COMPILER-RT (LIBGCC)"
   compiler-rt arm
+  compiler-rt mips32
   compiler-rt x86-32
   compiler-rt x86-64
 }