main: add cached GOROOT to info subcommand

This is necessary for an upcoming VS Code extension to support TinyGo,
and may be useful for other people wanting to use proper autocompletion
etc in their IDE.

main.go

@@ -940,12 +940,18 @@ func main() {
 			fmt.Fprintln(os.Stderr, err)
 			os.Exit(1)
 		}
+		cachedGOROOT, err := loader.GetCachedGoroot(config)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
 		fmt.Printf("LLVM triple:       %s\n", config.Triple())
 		fmt.Printf("GOOS:              %s\n", config.GOOS())
 		fmt.Printf("GOARCH:            %s\n", config.GOARCH())
 		fmt.Printf("build tags:        %s\n", strings.Join(config.BuildTags(), " "))
 		fmt.Printf("garbage collector: %s\n", config.GC())
 		fmt.Printf("scheduler:         %s\n", config.Scheduler())
+		fmt.Printf("cached GOROOT:     %s\n", cachedGOROOT)
 	case "list":
 		config, err := builder.NewConfig(options)
 		if err != nil {