internal/pkg: optionally register binfmt

This transparently supports curing foreign exec artifacts.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/internal/testtool/main.go

@@ -24,6 +24,19 @@ func main() {
 	log.SetFlags(0)
 	log.SetPrefix("testtool: ")
 
+	if os.Getenv("HAKUREI_BINFMT") == "1" {
+		wantArgs := []string{"/interpreter", "/opt/bin/sample"}
+		if !slices.Equal(os.Args, wantArgs) {
+			log.Fatalf("Args: %q, want %q", os.Args, wantArgs)
+		}
+
+		if err := os.WriteFile("check", []byte("binfmt"), 0400); err != nil {
+			log.Fatal(err)
+		}
+
+		return
+	}
+
 	environ := slices.DeleteFunc(slices.Clone(os.Environ()), func(s string) bool {
 		return s == "CURE_JOBS="+strconv.Itoa(runtime.NumCPU())
 	})