fix(ci): export IMAGE_TAG variable for better clarity in build process

1 job for sub2api/v0.0.3 in 9 minutes and 2 seconds (queued for 4 seconds)
latest
Name Stage Failure
failed
sub2api Build
  -strictdups int
sanity check duplicate symbol contents during object file reading (1=warn 2=err).
-tmpdir directory
use directory for temporary files
-v print link trace
-w disable DWARF generation
The command '/bin/sh -c VERSION_VALUE="${VERSION}" && if [ -z "${VERSION_VALUE}" ]; then VERSION_VALUE="$(tr -d '\r\n' < ./cmd/server/VERSION)"; fi && DATE_VALUE="${DATE:-$(date -u +%Y-%m-%dT%H:%M:%SZ)}" && CGO_ENABLED=0 GOOS=linux go build -tags embed -ldflags="-s -w -X main.Version=${VERSION_VALUE} -X main.Commit=${COMMIT} -X main.Date=${DATE_VALUE} -X main.BuildType=release" -trimpath -o /app/sub2api ./cmd/server' returned a non-zero code: 1
Cleaning up project directory and file based variables
ERROR: Job failed: exit status 1