pkg/utils: fix compilation error for Windows

[AkihiroSuda]

What this PR does / why we need it: Fixes compilation for WIndows

Required for:

• https://github.com/containerd/nerdctl/pull/2642

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged): Fixes #246

Please check the following list:

• [ ] Does the affected code have corresponding tests, e.g. unit test, E2E test?
• [ ] Does this change require a documentation update?
• [ ] Does this introduce breaking changes that would require an announcement or bumping the major version?
• [ ] Do all new files have an appropriate license header?

[AkihiroSuda]

Can we get a new release?

[liulanzheng]

Can we get a new release?

v1.0.2 is ready.

[AkihiroSuda]

Thanks!