run-checks: update to match new argument syntax of ineffassign

[jhenstridge]

The ineffassign utility has changed its argument syntax so that the static checks fail with:

-: no Go files in .../src/github.com/snapcore/snapd
ineffassign: error during loading

To check the current package and all sub-packages, we now need to pass ./... as the argument (as outlined in gordonklaus/ineffassign#51).

[bboozzoo]

Thanks!

[mvo5]

Thank you

[jhenstridge]

This is failing the Go 1.9 unit test run with:

# golang.org/x/tools/go/analysis
../../../golang.org/x/tools/go/analysis/validate.go:119:8: undefined: strings.Builder
# golang.org/x/tools/go/packages
../../../golang.org/x/tools/go/packages/golist_overlay.go:547:7: undefined: strings.ReplaceAll

The changes to ineffassign add a dependency on golang.org/x/tools, which in turn depends on stdlib features not found in Go 1.9. I'm not sure of the best way around this part of the change. Maybe disabling the test on old Go would be appropriate?