CMake: Fix build with unversion_libname configuration

a162a3cb (Android: Add "unversioned_libname" configuration, 2014-04-23)
removed the version for shared libs on Android. This change updates
the generated CMake files to support that.

Change-Id: Ia6ef04872c664bd4c31546456a82730babed2910
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>