gen-lockedsig-cache: fix bad destination path joining
When copying the sstate-cache into the extensible SDK, if the source
path had a trailing / and the destination path did not, there would be a
missing / between the path and the subdirectory name, and you'd end up
with subdirectories like "sstate-cacheCentOS-6.7". There are functions
in os.path for this sort of thing so let's just use them and avoid the
problem.
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
