runtime: darwin builders failing on metrics changes

[prattmic]

All of the darwin builders are failing on one of the metrics changes that just went in.

The failing commit is one of golang.org/cl/246971, golang.org/cl/246972, golang.org/cl/246973.

I am attempting to repro on a gomote.

cc @mknyszek @aclements @golang/release

[prattmic]

https://golang.org/cl/246971 is the specific failing CL.

[gopherbot]

Change https://golang.org/cl/265157 mentions this issue: runtime: make sysMemStats' methods nosplit

[gopherbot]

Change https://golang.org/cl/265158 mentions this issue: runtime: revert commits 8ebc58..a8b28eb