cmd/link: set correct sizes for XCOFF outer symbols
This commit fixes the size of outer symbols like type.*.
Outer symbols cannot have a nil size on AIX or they will be
removed by ld as long as all their sub-symbols.
Change-Id: I68ff3ce5a3a034e3c3eb23431aba31245073cf20
Reviewed-on: https://go-review.googlesource.com/c/163999
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>