lint: set proper cache key for golangci-lint target

[crazy-max]

reported by @jsternberg

 > [lint-nydus golangci-lint 1/1] RUN --mount=target=/go/src/github.com/moby/buildkit     --mount=target=/root/.cache,type=cache,id=lint-cache-linux/arm64   xx-go --wrap &&   golangci-lint run --build-tags "nydus" &&   touch /golangci-lint.done:
61.01 cmd/buildkitd/main.go:17:46: directive `//nolint:staticcheck // SA1019 deprecated` is unused for linter "staticcheck" (nolintlint)
61.01   "github.com/containerd/containerd/pkg/seed" //nolint:staticcheck // SA1019 deprecated
61.01                                               ^
61.01 cmd/buildkitd/main.go:80:2: directive `//nolint:staticcheck // SA1019 deprecated` is unused for linter "staticcheck" (nolintlint)
61.01   //nolint:staticcheck // SA1019 deprecated
61.01   ^

Cache is shared across targets (default, labs, nydus) but should have its own key.

[jedevc]

Nice catch, I've also seen that weird linting error but never been able to catch why it was happening 🎉