Teach LNT about 64-bit Mips targets.

[dsanders]

LGTM

Could you mention what it fixes in the commit message? Particularly that it stops the SSE tests running (and failing due to lack of SSE).

lnt/trunk/lnt/tests/nt.py

def compute_run_make_variables(self):
                   arch == 'xscale'):
                 llvm_arch = 'ARM'
             elif arch in ('aarch64', 'arm64'):
                 llvm_arch = 'AArch64'
             elif arch.startswith('alpha'):
                 llvm_arch = 'Alpha'
             elif arch.startswith('sparc'):
                 llvm_arch = 'Sparc'
-            elif arch in ('mips', 'mipsel'):
+            elif arch in ('mips', 'mipsel', 'mips64', 'mips64el'):
                 llvm_arch = 'Mips'
 
         if llvm_arch is not None:
             make_variables['ARCH'] = llvm_arch
         else:
             warning("unable to infer ARCH, some tests may not run correctly!")
 
         # Add in any additional make flags passed in via --make-param.