cmd/go: for gccgo expect one fewer file in TestScript/list_swigcxx
cmd/go: for gccgo expect one fewer file in TestScript/list_swigcxx

One of the files in CompileGoFiles is actually _cgo_import.go, but
that file is only generated for gc, not for gccgo.

Change-Id: I87bb55552e1409cc57da8f35a32b37ce4a3df60c
Reviewed-on: https://go-review.googlesource.com/c/go/+/390895
Trust: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Bryan Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>

golang/go,golang/go,nawawi/go,nawawi/go,CAFxX/go,nawawi/go,CAFxX/go,golang/go,golang/go,CAFxX/go,CAFxX/go,CAFxX/go,nawawi/go,nawawi/go,golang/go,nawawi/go,CAFxX/go,golang/go,nawawi/go,golang/go,CAFxX/go,golang/go,CAFxX/go,nawawi/go