This reverts commit https://golang.org/cl/54030

Reason for revert: to not paint ourselves into a corner.
See https://github.com/golang/go/issues/23009

Fixes #23009
Updates #21255

Change-Id: I68caab078839b9d2bf645a7bbed8405a5a30cd22
Reviewed-on: https://go-review.googlesource.com/86435Reviewed-by: Ian Lance Taylor <iant@golang.org>