Add G204 rule for sys/execabs (#660)

* Add G204 rule for sys/execabs

* syntax error in testutils/sources.go

testutils/source.go

@@ -1368,6 +1368,24 @@ func main() {
 	err = cmd.Wait()
 	log.Printf("Command finished with error: %v", err)
 }`}, 0, gosec.NewConfig()},
+		{[]string{`
+// exec.Command from supplemental package sys/execabs
+// using variable arguments
+package main
+import (
+	"context"
+	"log"
+	"os"
+	exec "golang.org/x/sys/execabs"
+)
+func main() {
+	err := exec.CommandContext(context.Background(), os.Args[0], "5").Run()
+	if err != nil {
+		log.Fatal(err)
+	}
+	log.Printf("Command finished with error: %v", err)
+}
+`}, 1, gosec.NewConfig()},
 	}
 
 	// SampleCodeG301 - mkdir permission check