TARGET_OS_OSX is the right macro, but it also was only introduced
in 1.12.  For 1.11 and earlier a reasonable substitution is
TARGET_OS_IPHONE == 0.

Update #24161
Update #26355

Change-Id: I5f43c463d14fada9ed1d83cc684c7ea05d94c5f3
Reviewed-on: https://go-review.googlesource.com/124075
Run-TryBot: Keith Randall <khr@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>