Update status for mips big_integer_vm test.

tests/corelib/corelib.status

 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 [ $compiler == dart2dart]
 bool_from_environment2_test: Skip
 bool_from_environment_default_value_test: Skip
 bool_from_environment_test: Skip
 int_from_environment2_test: Skip
 int_from_environment3_test: Skip
@@ skipping 141 matching lines @@
 int_parse_radix_test: Fail, OK # Test contains errors but doesn’t mark them as expected
 list_insert_test: Fail, OK # Test contains errors but doesn’t mark them as expected
 list_removeat_test: Fail, OK # Test contains errors but doesn’t mark them as expected
 
 [ $compiler == dart2analyzer ]
 int_parse_radix_test: fail
 list_insert_test: fail
 list_removeat_test: fail
 
 [ $arch == simarm || $arch == simarm64 ]
-big_integer_vm_test: Skip # Timeout
+big_integer_vm_test: Skip # Timeout. Issue 20879
 
 [ $arch == simmips ]
 int_parse_radix_test: Skip # Timeout
-big_integer_vm_test: Skip # Timeout
+
+[ $arch == simmips || $arch == mips ]
+big_integer_vm_test: Skip # Timeout. Issue 20879
 
 [ $arch == simarm && $checked ]
 num_parse_test: Skip  # Pass, Timeout
 
 [ $compiler == dartanalyzer || $compiler == dart2analyzer ]
 error_stack_trace_test: StaticWarning, OK # Test generates errors on purpose.
 iterable_element_at_test: StaticWarning, OK # Test generates errors on purpose.
 num_clamp_test: StaticWarning, OK # Test generates errors on purpose.
 string_test: StaticWarning, OK # Test generates error on purpose.
 
 [ $compiler == dart2js && ($runtime == safari || $runtime == safarimobilesim) ]
 list_test/01: Fail # Safari bug: Array(-2) seen as dead code.
 
 [ $runtime == ie9 || $runtime == ie10 ]
 num_parse_test: RuntimeError  # Issue 15316
 num_parse_test/01: RuntimeError  # Issue 15316
 
 [ $system == windows && $arch == x64 ]
 stopwatch_test: Skip  # Flaky test due to expected performance behaviour.