cmd/compile,runtime: found pointer to free object on linux-amd64-noopt

[2022-09-02T20:14:40-3e11e61/linux-amd64-noopt](https://build.golang.org/log/b42c44f119bf5b24297bb66b54803e19c5750c89)
[2022-09-02T19:22:26-0fda8b1/linux-amd64-noopt](https://build.golang.org/log/1d3db4054eafde08de1ce5d2b5a8f585bbedc295)

Since I only saw this failure mode on the noopt builders, I figure it's some kind of compiler/runtime interaction.

CC @golang/compiler @golang/runtime 