CL 62593 broken TestExportedSymbols and TestUnexportedSymbols
because it started executing android test binary on host.
Make them run on android.

Hopefully fixes android build.

Change-Id: Ic0bb9f0cbbefca23828574282caa33a03ef72431
Reviewed-on: https://go-review.googlesource.com/62830
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Elias Naur <elias.naur@gmail.com>