cmd/dist: really skip the testsanitizers tests on Android

The test.bash script in misc/cgo/testsanitizers use GOOS, not GOHOSTOS.
Fix the dist check from gohostos to goos accordingly.

The error was masked on the builders because they run on a darwin host
where the sanitizers tests never ran.

With this change, the Android test suite completes successfully on
Android/amd64.

Change-Id: Id7690429f78c6ac7a26fc9118d913b719b565bb2
Reviewed-on: https://go-review.googlesource.com/35959


Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>