fix test file bug in basic runner

@mortenvp @petya2164, do you see any issues with this?

The issue is that i want test files to be in the ``project_repo/test`` directory, instead of the root of the repository.
But since ``find_or_declare`` (https://waf.googlecode.com/svn/docs/apidocs/Node.html#waflib.Node.Node.find_or_declare) only creates the file if it's not already in the build or the source folder, the test file is not created.