Update instructions to set RBE_AUTOCONF_ROOT (#842)
Update instructions to set RBE_AUTOCONF_ROOT (#842)

If this is not set, then the rbe_autoconfig simply errors out with a message that it needs to be set, but no explanation of what to set it *to*.

Co-authored-by: alex1545 <a692d86d429dac5ac53dc54062a8739caca03939@users.noreply.github.com>
bazelbuild/bazel-toolchains