base.Fatal(err)
	}

	gotmp, okGOTMP := add["GOTMPDIR"]
	if okGOTMP {
		if !filepath.IsAbs(gotmp) && gotmp != "" {
			base.Fatalf("go: GOTMPDIR must be an absolute path")
		}
	}

	updateEnvFile(add, nil)
}

func runEnvU(args []string) {
	// Process and sanity-check command line.
	if len(args) == 0 {
		base.Fatalf("go: 'go env -u' requires an argument")
	}
	del := make(map[string]bool)