base: Bump disk size

'el8stream' builds are complaining about disk space, so let's bump it.

Signed-off-by: Marcin Sobczyk <msobczyk@redhat.com>

makefiles/vars.mk

@@ -11,7 +11,7 @@ REPO_ROOT := "http://mirror.centos.org/centos/8-stream/"
 _USING_ISO := $(findstring .iso,$(INSTALL_URL))
 # The virtual size of the disk.
 # Since qcows are sparse they only use as much space as was really written to them.
-DISK_SIZE := 22G
+DISK_SIZE := 24G
 # Whether or not to run 'virt-sparsify' on the base image.
 # This reduces the image size significantly,
 # but requires the same amount of free space available as defined by 'DISK_SIZE' variable.