Build for arm64

[zchef2k]

I deployed an arm-based k3s cluster and wanted to continue to use this plugin but ran into a compatibility issue. This simply builds the Go package for arm64, I suspect you all would want to handle this differently. The included Github workflow builds the container for arm64, also.

In my helm values I changed the repo location to my Github package. I am able to issue LE certs now. Running pod describe, if it's helpful:

Name:             cert-manager-ns1-cert-manager-webhook-ns1-6b58744f5-qh7wk
Namespace:        cert-manager
Priority:         0
Service Account:  cert-manager-ns1-cert-manager-webhook-ns1
Node:             re.dac.ted/re.da.ct.ed
Start Time:       Mon, 26 Jun 2023 13:21:14 -0400
Labels:           app=cert-manager-webhook-ns1
                  pod-template-hash=6b58744f5
                  release=cert-manager-ns1
Annotations:      <none>
Status:           Running
IP:               10.42.4.7
IPs:
  IP:           10.42.4.7
Controlled By:  ReplicaSet/cert-manager-ns1-cert-manager-webhook-ns1-6b58744f5
Containers:
  cert-manager-webhook-ns1:
    Container ID:  containerd://abfdb337a2dc4f448e6d118e974c31d508d0836760b3e7b278767fcdc500bd29
    Image:         ghcr.io/zchef2k/cert-manager-webhook-ns1:latest
    Image ID:      ghcr.io/zchef2k/cert-manager-webhook-ns1@sha256:d9eb39049535070b497767c2332bdf21fa2f8b94865d05a7a6acafe182ec6241
    Port:          8443/TCP
    Host Port:     0/TCP
    Args:
      --secure-port=8443
      --tls-cert-file=/tls/tls.crt
      --tls-private-key-file=/tls/tls.key
    State:          Running
      Started:      Mon, 26 Jun 2023 13:21:17 -0400
    Ready:          True
    Restart Count:  0
    Liveness:       http-get https://:https/healthz delay=0s timeout=1s period=10s #success=1 #failure=3
    Readiness:      http-get https://:https/healthz delay=0s timeout=1s period=10s #success=1 #failure=3
    Environment:
      GROUP_NAME:  acme.nsone.net
    Mounts:
      /tls from certs (ro)
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-trh5p (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  certs:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  cert-manager-ns1-cert-manager-webhook-ns1-webhook-tls
    Optional:    false
  kube-api-access-trh5p:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
QoS Class:                   BestEffort
Node-Selectors:              <none>
Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:                      <none>

Please let me know if you're interested in including this into your release and how you'd like this contributed.