fadf8c71 (git_remote_helpers: force rebuild if python version changes, 2013-01-20)
started using a marker file to keep track of the version of Python interpreter
used for the last build, but forgot to remove it when asked to "make clean".
Acked-by: John Keeping <email@example.com>
Signed-off-by: Junio C Hamano <firstname.lastname@example.org>