runtime: align m.procid to 8 bytes on 32-bit systems
https://go-review.googlesource.com/c/go/+/383434 started using
atomic Load64 on this field, which breaks 32 bit platforms which
require 64-bit alignment of uint64s that are passed to atomic operations.
Not sure why this doesn't break everywhere, but I saw it break on
my laptop during all.bash.
Change-Id: Ida27b23068b3cc7208fce3c97b69a464ccf68209
Reviewed-on: https://go-review.googlesource.com/c/go/+/399754
Run-TryBot: Keith Randall <khr@golang.org> Reviewed-by: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Keith Randall <khr@google.com>