build-rootfs: Relocate misplaced PAM libs

Some packages, notably _systemd_, place their PAM modules in
`/usr/lib64/security` instead of `/usr/lib/security`.  PAM only seems to
look in the latter location, though, so anything in the former needs to
be moved in order to be used.

build-rootfs.sh

@@ -90,8 +90,7 @@ qemu-${target%%-*} \
     -f /mnt/gentoo/etc/ld.so.conf
 
 if [ -d /mnt/gentoo/lib64/security ]; then
-    find /mnt/gentoo/lib64/security -name 'pam_*.so' \
-        -exec mv -t /mnt/gentoo/lib/security {} +
+    mv /mnt/gentoo/lib64/security/pam_*.so /mnt/gentoo/lib/security/
 fi
 
 rm -f /mnt/gentoo/lib/tmpfiles.d/provision.conf

overlay/usr/lib/systemd/sshd.service.d/no-keygen.conf

@@ -1,2 +0,0 @@
-[Service]
-ExecStartPre=