tf/asg: Increase root block device size

The default root block device for Fedora EC2 instances is only 10 GiB.
This is insufficient for many jobs, especially those that build large
container images.

terraform/asg.tf

@@ -65,6 +65,14 @@ resource "aws_launch_template" "k8s-aarch64" {
   private_dns_name_options {
     hostname_type = "resource-name"
   }
+
+  block_device_mappings {
+    device_name = "/dev/sda1"
+
+    ebs {
+      volume_size = 64
+    }
+  }
 }
 
 resource "aws_autoscaling_group" "k8s-aarch64" {