We have an optimization for this specific pattern, but it's really just
a hack. With the addition of unsafe.Add in Go 1.17 we can directly
specify the intent instead and eventually remove this special case.
The code is also easier to read.
Scan globals conservatively by reading writable sections from the PE
header.
I'd like to get rid of needing to precisely scan globals eventually, and
this brings us one step closer. It also avoids a bug with ThinLTO on
Windows.
