put the loplugin output files in the workdir

so that the next time I accidentally leave one turned on, and commit it,
the buildbots will clean up naturally the next time they run 'make
clean'

Change-Id: Ia09dea9c272c322c7e2773c5458cb54aceb50dd1

compilerplugins/clang/unusedmethods.py

@@ -33,7 +33,7 @@ def normalizeTypeParams( line ):
 # primary input loop
 # --------------------------------------------------------------------------------------------
 
-with io.open("loplugin.unusedmethods.log", "rb", buffering=1024*1024) as txt:
+with io.open("workdir/loplugin.unusedmethods.log", "rb", buffering=1024*1024) as txt:
     for line in txt:
         tokens = line.strip().split("\t")
         if tokens[0] == "definition:":