fix(kaniko): supply build args {in ci,locally}

since the switch to kaniko as a container image builder, proper
BUILD_DATE and VCS_REF values previously filled in by a build hook were
left empty. that changes now.

.drone.yml

@@ -29,6 +29,9 @@ steps:
   settings:
     dockerfile: Dockerfile
     context: .
+    args:
+      - BUILD_DATE="$(date -u +"%Y-%m-%dT%H:%M:%SZ")"
+      - VCS_REF=${DRONE_COMMIT_SHA:0:7}
   when:
     ref:
     - "refs/heads/feature-**"
@@ -43,6 +46,9 @@ steps:
   settings:
     dockerfile: Dockerfile
     context: .
+    args:
+      - BUILD_DATE="$(date -u +"%Y-%m-%dT%H:%M:%SZ")"
+      - VCS_REF=${DRONE_COMMIT_SHA:0:7}
     tags:
     - latest
     - linux-amd64

Makefile

@@ -8,7 +8,9 @@ dargskaniko = run --rm -it -w=$(kanikowdir) -v $$PWD:$(kanikowdir)
 kanikoexecutorimg = gcr.io/kaniko-project/executor@sha256:6ecc43ae139ad8cfa11604b592aaedddcabff8cef469eda303f1fb5afe5e3034
 kanikowdir = /src
 kanikocontext = .
-kanikoargs = -f=$(dfile) -c=$(kanikocontext) --use-new-run --snapshotMode=redo --no-push
+kanikoargs = -f=$(dfile) -c=$(kanikocontext) --use-new-run --snapshotMode=redo --build-arg BUILD_DATE=$(build_date) --build-arg VCS_REF=$(vcs_ref) --no-push
+vcs_ref = $$(git rev-parse --short HEAD)
+build_date= $$(date -u +"%Y-%m-%dT%H:%M:%SZ")
 hadolintimg = hadolint/hadolint:v2.7.0-alpine
 hadolintargs = run --rm -i -v $$PWD/.hadolint.yaml:/root/.config/hadolint.yaml