system/[various]: last SPDX license fixes

system/abuild/APKBUILD

system/busybox/APKBUILD

system/clang/APKBUILD

system/db/APKBUILD

system/easy-kernel/APKBUILD

system/fakeroot/APKBUILD

system/fortify-headers/APKBUILD

system/iproute2/APKBUILD

system/libarchive/APKBUILD

system/libc-dev/APKBUILD

system/libedit/APKBUILD

system/linux-pam/APKBUILD

system/llvm4/APKBUILD

system/lutok/APKBUILD

system/mkinitfs/APKBUILD

system/openssl/APKBUILD

system/perl/APKBUILD

system/sp/APKBUILD

system/vim/APKBUILD

system/xz/APKBUILD