`GOTOOLDIR`'s value is set to wrong path after installing `gccgo`. How do I change it back or append path to another directory to it?

After installing gccgo the command go tool toolname stopped working due to $GOTOOLDIR being changed to one used by gccgo. It now prints go tool: no such tool "toolname" for every tool that is inside go/pkg/tool/linux_amd64/.

Can I change $GOTOOLDIR back to the old value? Or can I append the old value to it so, that go tool could look for tools in both directories?