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

pnacl/driver/pnacl-ld.py

 #!/usr/bin/python
 # Copyright (c) 2012 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 # IMPORTANT NOTE: If you make local mods to this file, you must run:
 #   %  pnacl/build.sh driver
 # in order for them to take effect in the scons build.  This command
 # updates the copy in the toolchain/ tree.
 #
@@ skipping 169 matching lines @@
   ( '(-export-dynamic)', AddToBCLinkFlags),
 
   ( '-?-soname=(.*)',             "env.set('SONAME', $0)"),
   ( ('-?-soname', '(.*)'),        "env.set('SONAME', $0)"),
 
   ( '(-M)',                       AddToBCLinkFlags),
   ( '(-t)',                       AddToBCLinkFlags),
   ( ('(-y)','(.*)'),              AddToBCLinkFlags),
   ( ('(-defsym)','(.*)'),         AddToBCLinkFlags),
 
-  ( '-melf_nacl',          "env.set('ARCH', 'X8632')"),
-  ( ('-m','elf_nacl'),     "env.set('ARCH', 'X8632')"),
-  ( '-melf64_nacl',        "env.set('ARCH', 'X8664')"),
-  ( ('-m','elf64_nacl'),   "env.set('ARCH', 'X8664')"),
-  ( '-marmelf_nacl',       "env.set('ARCH', 'ARM')"),
-  ( ('-m','armelf_nacl'),  "env.set('ARCH', 'ARM')"),
+  ( '-melf_nacl',            "env.set('ARCH', 'X8632')"),
+  ( ('-m','elf_nacl'),       "env.set('ARCH', 'X8632')"),
+  ( '-melf64_nacl',          "env.set('ARCH', 'X8664')"),
+  ( ('-m','elf64_nacl'),     "env.set('ARCH', 'X8664')"),
+  ( '-marmelf_nacl',         "env.set('ARCH', 'ARM')"),
+  ( ('-m','armelf_nacl'),    "env.set('ARCH', 'ARM')"),
+  ( '-mmipselelf_nacl',      "env.set('ARCH', 'MIPS32')"),
+  ( ('-m','mipselelf_nacl'), "env.set('ARCH', 'MIPS32')"),
 
   ( ('(-?-wrap)', '(.+)'), AddToBCLinkFlags),
   ( ('(-?-wrap=.+)'),      AddToBCLinkFlags),
 
   # NOTE: For scons tests, the code generation fPIC flag is used with pnacl-ld.
   ( '-fPIC',               "env.set('PIC', '1')"),
 
   # This controls LTO optimization.
   # opt does not support -Os but internally it is identical to -O2
   # opt also does not support -O4 but -O4 is how you ask clang for LTO, so we
@@ skipping 273 matching lines @@
   -O<opt-level>               Optimize output file
   -M, --print-map             Print map file on standard output
   --whole-archive             Include all objects from following archives
   --no-whole-archive          Turn off --whole-archive
   -s, --strip-all             Strip all symbols
   -S, --strip-debug           Strip debugging symbols
   --undefined SYMBOL          Start with undefined reference to SYMBOL
 
   -help | -h                  Output this help.
 """