utils/scanpypi: correctly handle license dirs in subdirs for .hash files

utils/scanpypi: correctly handle license dirs in subdirs for .hash files

create_hash_file() used basename(licensefile) when it writes the entry for
the license file in the .hash, which is obviously not correct when license
file is locate in a sub directory.

Instead copy the logic from __create_mk_license() to strip the directory
prefix from the absolute filename instead.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Reviewed-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>