gen-lockedsig-cache: ensure symlinks are dereferenced
If you set up a local mirror in SSTATE_MIRRORS then you can end up with
symlinks in SSTATE_DIR rather than real files. We don't want these
symlinks in the sstate-cache prodcued by gen-lockedsig-cache, so
dereference any symlinks before copying.
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>