Update the linker's XCOFF writer to handle coverage counter sections
properly; they need to be treated as bss, not data. Fixes a problem
with the aix-ppc64 builder introduced in CL 401235), e.g.
"runtime.covctrs: A symbol with type XTY_SD must be in a .text or
.data section".
Updates #51430.
Change-Id: I3fc385a37e2549c46cc7cc3b4718af989a36752a
Reviewed-on: https://go-review.googlesource.com/c/go/+/435335 Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Than McIntosh <thanm@google.com> Reviewed-by: David Chase <drchase@google.com>