Fix broken link generation for KERNEL projects.
Using $1 in projectsmirrors sub was still referencing the caller $1
instead of the remaining args of projectsmirrors sub.
Use shift and put the second arg of projectsmirrors sub in $append to
correctly handle the sub args.
Fixes: 465cf35888 ("scripts/download.pl: detach mirror URLs from script file")
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>