assume-no-moving-gc issue with go 1.18

[yglcode]

"go install github.com/cloudflare/tubular/cmd/tubectl@latest" will get a tubectl with the following warning:
"
panic: Something in this program imports go4.org/unsafe/assume-no-moving-gc to declare that it assumes a non-moving garbage collector, but your version of go4.org/unsafe/assume-no-moving-gc hasn't been updated to assert that it's safe against the go1.18 runtime. If you want to risk it, run with environment variable ASSUME_NO_MOVING_GC_UNSAFE_RISK_IT_WITH=go1.18 set. Notably, if go1.18 adds a moving garbage collector, this program is unsafe to use.
"
upgrade go4.org/unsafe/assume-no-moving-gc will fix it