mark variant unusable with mipspro

[SVN r25223]

status/explicit-failures-markup.xml

@@ -1145,6 +1145,10 @@ for more information.
         </test>
     </library>
     <library name="variant">
+        <mark-unusable>
+            <toolset name="mipspro"/>
+            <note refid="2"/>
+        </mark-unusable>
         <test name="recursive_variant_test">
             <mark-failure>
                 <toolset name="borland"/>