Ok I got a working slackbuild
Not sure why but ,,
I removed this from the original slackbuild , edit the source number ect .
#removed
mkdir -p $PKG/usr/doc/$PRGNAM-$VERSION
cp -a \
COPYING* README* \
$PKG/usr/doc/$PRGNAM-$VERSION
cat $CWD/$PRGNAM.SlackBuild > $PKG/usr/doc/$PRGNAM-$VERSION/$PRGNAM.SlackBuild
Then the resulting slackbuild works as intended