Problem is in file linux.install:
# remove old initcpio
rm -f /boot/initramfs-${KERNEL_BASE}*-${ARCH}*.img
rm -f /boot/initramfs-${BASEVER}-${ARCH}*.img
I suggest removing the wildcard * after $KERNEL_BASE. Also, I think the second 'rm' doesn't serve a purpose, and can be removed as well.