feat: add GNOROOT environment variables

Adds the ability to obtain the root directory from the GNOROOT environment variable. If this variable is not set, the root directory is then guessed using the go list command.

Signed-off-by: gfanton <8671905+gfanton@users.noreply.github.com>

gnovm/cmd/gno/util.go

@@ -105,10 +105,16 @@ func fmtDuration(d time.Duration) string {
 }
 
 func guessRootDir() string {
+	// try to get the root directory from the GNOROOT environment variable.
+	if rootdir := os.Getenv("GNOROOT"); rootdir != "" {
+		return filepath.Clean(rootdir)
+	}
+
+	// if GNOROOT is not set, try to guess the root directory using the `go list` command.
 	cmd := exec.Command("go", "list", "-m", "-mod=mod", "-f", "{{.Dir}}", "github.com/gnolang/gno")
 	out, err := cmd.CombinedOutput()
 	if err != nil {
-		log.Fatal("can't guess --root-dir, please fill it manually.")
+		log.Fatal("can't guess --root-dir, please fill it manually or define the GNOROOT environment variable globally.")
 	}
 	rootDir := strings.TrimSpace(string(out))
 	return rootDir