Explicitly add linux and mkinitcpio to packages.x86_64

linux only gets pulled in because of broadcom-wl and mkinitcpio (usually) gets pulled in by linux.

configs/releng/packages.x86_64

@@ -33,6 +33,7 @@ iwd
 jfsutils
 kitty-terminfo
 lftp
+linux
 linux-atm
 linux-firmware
 lsscsi
@@ -43,6 +44,7 @@ man-pages
 mc
 mdadm
 memtest86+
+mkinitcpio
 mkinitcpio-nfs-utils
 mtools
 nano