Build broken on v1 branch

Build is broken on the v1 branch
```
# oras.land/oras-go/pkg/context
go: no such tool "covdata"
+ rm -rf .test/
Error: make: *** [Makefile:6: test] Error 1
Error: Process completed with exit code 2.
```

https://github.com/oras-project/oras-go/actions/runs/21375691308/job/61531155517?pr=1099

It may be related to the pull request https://github.com/oras-project/oras-go/pull/1099 but I doubt it.