Fixes parallel make where each invocation of swig was writing and deleting the same file resulting in lots of the newly introduced warning messages: On exit, could not delete file xxx.py: No such file or directory
git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk@12395 626c5289-ae23-0410-ae9c-e8d60b6d4f22