buildx failed with: ERROR: failed to solve: process "/bin/sh -c export BUILD_TIME=$(date -u +\"%Y-%m-%dT%H:%M:%SZ\"); go build -o backend -ldflags \"-X exusiai.dev/backend-next/internal/pkg/bininfo.Version=$VERSION -X exusiai.dev/backend-next/internal/pkg/bininfo.BuildTime=$BUILD_TIME\" ." did not complete successfully: exit code: 1