fix cd gnovm; make imports

[moul]

#3455 introduced a bug when we run cd gnovm; make imports.

21:39:15 ~  cd go/src/github.com/gnolang/gno/gnovm
21:39:20 gno/gnovm  make imports
go run -modfile ../misc/devdeps/go.mod golang.org/x/tools/cmd/goimports -w .
pkg/gnolang/testdata/corpra/parsefile/a.go:5:1: expected declaration, found ')'
pkg/gnolang/testdata/corpra/parsefile/bug_3014_redefine.go:2:1: illegal character U+FFFC ''
pkg/gnolang/testdata/corpra/parsefile/bug_3014_redefine2.go:2:1: illegal character U+FFFC ''
pkg/gnolang/testdata/corpra/parsefile/bug_3014_redefine3.go:2:1: illegal character U+FFFC ''
pkg/gnolang/testdata/corpra/parsefile/bug_3014_redefine4.go:2:1: illegal character U+FFFC ''
pkg/gnolang/testdata/corpra/parsefile/bug_3014_redefine5.go:2:1: illegal character U+FFFC ''
pkg/gnolang/testdata/corpra/parsefile/bug_3014_redefine6.go:2:1: illegal character U+FFFC ''
exit status 2
make: *** [Makefile:62: imports] Error 1

We need to fix the make imports command to ignore those intentionally invalid files or move them elsewhere so that they are excluded.

Additionally, we need to ensure that the CI checks for make imports result in success, similar to how we handle make fmt.

[thehowl]

testdata is normally excluded by go tools, so it's weird it's caught by goimports.

[thehowl]

Maybe we can turn it into some kind of go list -f '{{ join .BuildFiles "\n" }}' | xargs goimports -w

[moul]

Fixed in #3602

We will close this issue until we encounter a similar problem in the future.