[infer][java] do not pass -Werror to javac

Summary:
@public
We do not want Infer to die because javac emits a warning.

Closes https://github.com/facebook/infer/issues/18.

Written together with irp.

Test Plan:
This used to fail but now works:

  git clone https://github.com/igniterealtime/Smack.git
  cd Smack
  infer -- gradle build

infer/bin/inferlib.py

@@ -151,7 +151,10 @@ def get_javac_args(args):
         return None
     else:
         # replace any -g:.* flag with -g to preserve debugging symbols
-        return map(lambda arg: '-g' if '-g:' in arg else arg, javac_args)
+        args = map(lambda arg: '-g' if '-g:' in arg else arg, javac_args)
+        # skip -Werror
+        args = filter(lambda arg: arg != '-Werror', args)
+        return args
 
 
 def remove_infer_out(infer_out):