runtime: segfault on linux/mips

[aclements]

CL 85887 started causing linux/mips to segfault during the bootstrap process. I haven't looked into why yet.

linux/mipsle is also regularly flaking with a segfault later during testing. The root cause may be the same.

/cc @cherrymui

[aclements]

The problem on linux/mips is that the &untracked pointer passed to persistentalloc by mallocinit isn't 8-byte aligned, so the atomic add in mSysStatInc crashes.

[gopherbot]

Change https://golang.org/cl/95695 mentions this issue: runtime: ensure sysStat for mheap_.arenas is aligned